What are normal TSH levels for thyroid function. How do high TSH levels indicate hypothyroidism. What symptoms are associated with abnormal TSH levels. How does thyroid hormone regulation impact overall health.

The Role of TSH in Thyroid Function

Thyroid stimulating hormone (TSH) plays a crucial role in maintaining the body’s homeostasis. Produced by the pituitary gland, TSH acts as a messenger, instructing the thyroid gland to produce hormones that regulate various bodily functions. Understanding TSH levels is essential for diagnosing and treating thyroid disorders.

TSH primarily stimulates the production of two key thyroid hormones:

• Triiodothyronine (T3)
• Thyroxine (T4)

These hormones are responsible for regulating:

• Metabolic rate
• Body temperature
• Brain development
• Heart function
• Muscle control
• Digestive processes

Given the wide-ranging effects of thyroid hormones, maintaining proper TSH levels is crucial for overall health and well-being.

Decoding TSH Levels: What’s Normal and What’s Not

Determining normal TSH levels has been a subject of ongoing debate in the medical community. While there is some variation, most healthcare providers consider the following ranges:

• Normal TSH range: 0.5 to 4.5 or 5 mIU/L
• Subclinical hypothyroidism: 4.5 to 10 mIU/L
• Overt hypothyroidism: 10 mIU/L or higher

Is there a one-size-fits-all approach to interpreting TSH levels? Not necessarily. What’s considered normal can vary from person to person, and factors such as age, sex, and overall health status can influence TSH levels. This is why healthcare providers often consider TSH results in conjunction with other thyroid hormone tests and clinical symptoms.

The Importance of Comprehensive Thyroid Testing

While TSH is a valuable indicator of thyroid function, it’s not the only piece of the puzzle. To get a complete picture of thyroid health, doctors often recommend additional tests, including:

• Free T4
• Total T3
• Thyroid antibodies (in cases of suspected autoimmune thyroid disorders)
• Thyroid ultrasound (to examine the gland’s structure)

By examining these factors together, healthcare providers can make more accurate diagnoses and develop tailored treatment plans.

High TSH Levels: Unraveling the Causes and Implications

When TSH levels are elevated, it often indicates that the thyroid gland is underactive, a condition known as hypothyroidism. But why does this happen?

In a normal feedback loop, the thyroid gland produces sufficient hormones, signaling the pituitary to reduce TSH production. However, when the thyroid isn’t producing enough hormones, the pituitary responds by increasing TSH output in an attempt to stimulate more thyroid hormone production.

Common Causes of High TSH Levels

• Hashimoto’s thyroiditis (an autoimmune condition)
• Iodine deficiency
• Radiation therapy to the neck area
• Thyroid surgery
• Certain medications (e.g., lithium, amiodarone)
• Congenital hypothyroidism (present at birth)

How do high TSH levels manifest in terms of symptoms? Patients with elevated TSH may experience:

• Fatigue and low energy
• Unexpected weight gain
• Sensitivity to cold
• Dry skin and hair
• Constipation
• Depression
• Irregular menstrual cycles
• Difficulty concentrating

It’s important to note that these symptoms can overlap with other conditions, which is why laboratory testing is crucial for an accurate diagnosis.

Low TSH Levels: Implications for Hyperthyroidism

While high TSH levels often indicate hypothyroidism, low TSH levels can suggest an overactive thyroid, or hyperthyroidism. In this case, the thyroid is producing excess hormones, causing the pituitary to reduce TSH production.

Potential Causes of Low TSH Levels

• Graves’ disease (an autoimmune disorder)
• Toxic multinodular goiter
• Thyroiditis (inflammation of the thyroid gland)
• Excessive iodine intake
• Overmedication with thyroid hormone replacement therapy

What symptoms might accompany low TSH levels? Individuals with hyperthyroidism may experience:

• Unexplained weight loss
• Rapid heartbeat or palpitations
• Increased appetite
• Anxiety and irritability
• Tremors
• Heat intolerance
• Excessive sweating
• Changes in menstrual patterns

As with hypothyroidism, these symptoms can be nonspecific, emphasizing the need for proper diagnostic testing.

The Complexity of TSH Interpretation: Beyond the Numbers

Interpreting TSH levels isn’t always straightforward. Various factors can influence TSH readings, potentially leading to misdiagnosis if not carefully considered.

Factors Affecting TSH Levels

• Time of day (TSH levels naturally fluctuate throughout the day)
• Recent illness or stress
• Pregnancy
• Certain medications (e.g., steroids, dopamine agonists)
• Age (TSH tends to increase with age)
• Ethnicity (some populations have naturally higher or lower TSH levels)

How can healthcare providers ensure accurate interpretation of TSH results? By considering the following:

1. Evaluating TSH in conjunction with free T4 and T3 levels
2. Assessing the patient’s clinical symptoms
3. Taking into account the patient’s medical history and current medications
4. Repeating tests to confirm results, especially in borderline cases
5. Considering additional diagnostic tools, such as thyroid antibody tests or imaging studies

This comprehensive approach helps avoid misdiagnosis and ensures that patients receive appropriate treatment.

Treatment Approaches for Abnormal TSH Levels

Once a thyroid disorder is diagnosed based on TSH and other thyroid function tests, treatment options vary depending on the specific condition and its severity.

Treating Hypothyroidism (High TSH)

The primary treatment for hypothyroidism is thyroid hormone replacement therapy. This typically involves taking a synthetic form of thyroxine (T4) called levothyroxine. The goal is to bring TSH levels back into the normal range and alleviate symptoms.

How is the dosage determined? Doctors usually start with a low dose and gradually increase it based on regular TSH monitoring. This approach helps avoid overtreatment, which can lead to symptoms of hyperthyroidism.

Managing Hyperthyroidism (Low TSH)

Treatment for hyperthyroidism depends on the underlying cause and may include:

• Antithyroid medications (e.g., methimazole, propylthiouracil)
• Radioactive iodine therapy
• Beta-blockers to manage symptoms like rapid heart rate
• In some cases, thyroid surgery (thyroidectomy)

The choice of treatment depends on factors such as the patient’s age, the severity of hyperthyroidism, and any coexisting medical conditions.

Lifestyle Considerations for Thyroid Health

While medication is often necessary for managing thyroid disorders, lifestyle factors can also play a role in supporting thyroid function and overall well-being.

Dietary Considerations

Can diet impact thyroid function? While no specific diet has been proven to cure thyroid disorders, certain nutrients are important for thyroid health:

• Iodine: Essential for thyroid hormone production
• Selenium: Supports thyroid hormone metabolism
• Zinc: Aids in thyroid hormone synthesis
• Iron: Necessary for thyroid hormone production

It’s important to note that excessive intake of certain foods, such as those high in goitrogens (e.g., soy, cruciferous vegetables), may interfere with thyroid function in some individuals. However, moderate consumption as part of a balanced diet is generally considered safe.

Stress Management and Exercise

Chronic stress can potentially impact thyroid function. Incorporating stress-reduction techniques such as meditation, yoga, or regular exercise may help support overall endocrine health.

How does exercise benefit thyroid function? Regular physical activity can:

• Improve metabolism
• Enhance mood and energy levels
• Help manage weight, which can be challenging with thyroid disorders
• Potentially increase thyroid hormone production and sensitivity

However, it’s important for individuals with thyroid disorders to consult their healthcare provider before starting a new exercise regimen, as thyroid function can affect exercise tolerance and recovery.

The Future of Thyroid Diagnostics and Treatment

As our understanding of thyroid function continues to evolve, new approaches to diagnosis and treatment are emerging. What advancements can we expect in the field of thyroid health?

Personalized Medicine in Thyroid Care

Researchers are exploring ways to tailor thyroid treatment based on individual genetic profiles and other biomarkers. This personalized approach may lead to more precise dosing of thyroid medications and better management of symptoms.

Advanced Imaging Techniques

New imaging technologies, such as high-resolution ultrasound and molecular imaging, are improving the detection and characterization of thyroid nodules and cancers. These advancements may lead to earlier diagnosis and more targeted treatments.

Novel Therapeutic Approaches

Ongoing research is investigating new treatment options for thyroid disorders, including:

• Thyroid hormone analogs that may offer more stable hormone levels
• Immunomodulatory therapies for autoimmune thyroid conditions
• Gene therapies targeting specific thyroid dysfunctions

These developments hold promise for improving the lives of individuals with thyroid disorders and may provide alternatives for those who don’t respond well to current treatments.

The Importance of Regular Thyroid Monitoring

Given the complex nature of thyroid function and its impact on overall health, regular monitoring is crucial for individuals with known thyroid disorders or those at risk.

Who Should Be Screened for Thyroid Disorders?

While universal screening for thyroid disorders is not currently recommended, certain groups may benefit from regular testing:

• Women over 60
• Individuals with a family history of thyroid disorders
• People with autoimmune conditions (e.g., type 1 diabetes, celiac disease)
• Individuals who have received radiation therapy to the head or neck
• Pregnant women or those planning to become pregnant

How often should thyroid function be checked? For those on thyroid medication, testing is typically done every 6-12 months, or more frequently when adjusting dosages. Individuals without known thyroid issues but with risk factors may benefit from screening every 3-5 years.

The Role of Patient Advocacy

Patients play a crucial role in managing their thyroid health. It’s important to:

• Keep track of symptoms and report changes to healthcare providers
• Adhere to prescribed medication regimens
• Attend regular follow-up appointments
• Educate oneself about thyroid health and available treatment options

By taking an active role in their care, patients can work with their healthcare providers to achieve optimal thyroid function and overall well-being.

Understanding TSH levels and their implications is crucial for diagnosing and managing thyroid disorders. While interpreting these results can be complex, a comprehensive approach that considers multiple factors can lead to accurate diagnosis and effective treatment. As research in thyroid health continues to advance, we can look forward to more personalized and targeted approaches to thyroid care, improving outcomes for individuals affected by these common endocrine disorders.

What Low TSH or High TSH Levels Could Mean

Think of your thyroid gland as a clearinghouse in which information runs in and out, to make sure your entire body achieves the balance of homeostasis.

Thyroid stimulating hormone (TSH) is produced by your brain’s pituitary gland and sent to your thyroid, to make sure that a state of equilibrium known as homeostasis occurs.

TSH tells your thyroid to produce more or fewer hormones, specifically triiodothyronine (T3) and thyroxine (T4), to make sure you’re operating optimally. These two hormones regulate many important aspects of your body, including metabolic rate, body temperature, and brain development.

Because the right amounts of T3 and T4 are responsible for helping maintain a smoothly functioning body in so many ways, understanding high, low, and normal levels of TSH is vital.

What Is Homeostasis?

Homeostasis and the endocrine system are based on a negative feedback system. When any end organ produces a hormone, these hormones then make their way back to the hypothalamus and the pituitary gland, so that the brain and pituitary gland know there’s an adequate amount of hormone being made.

If one of these organs is damaged, such as in autoimmune thyroid disease, and the thyroid gland is no longer making an adequate amount of thyroid hormone, this lower level is then detected by the hypothalamus in the brain. Therefore, a large amount of TSH is released in an attempt to produce more thyroid hormone from the thyroid gland.

What to Know About TSH Levels

Most commonly, providers use TSH levels to guide therapy to ensure that a person is producing the right levels of thyroid hormone. It’s important to look not only at TSH test results, but also free T4 and total T3, which could provide more accurate numbers and present a more comprehensive picture of what’s going on and for your doctor to figure out the right treatment plan.

In addition to blood tests, it’s important that your doctor knows the full picture of your presenting symptoms and when they occur, plus any medications or supplements you may be taking. To get to the bottom of what your issue may be, it’s possible that your doctor may order further tests, including a thyroid ultrasound.

Since TSH is responsible for the creation of hormones T3 and T4, which help regulate so much of your body, and because there are so many factors at play in creation or suppression of these hormones, using TSH data serves as the beginning of any thorough diagnosis and treatment plan. It can be confusing, especially considering what’s really a normal range for one person is not for another, and that levels will shift for many reasons.

For example, Joseph Winchell, M.D., family medicine physician at Mount Carmel Medical Group in Pickerington, OH, references a situation in which suppressed TSH is shown via testing. The physician’s initial reaction would be to reduce therapy. However, after checking free T4 or total T3, the full picture shows levels in the normal range.

What are Normal TSH Levels?

It’s an ongoing debate. Ultimately, the standard of care is to treat into the goal range for TSH, which is typically between 0.5 and 4.5 or 5.

A TSH level of 10 mIU/L or higher is typically indicative of hypothyroidism. A TSH level of 4.5 to 10 mIU/L is considered indicative of subclinical hypothyroidism.

If you visit your doctor complaining of thyroid issues, worried by symptoms such as fatigue and the inability to lose weight, it’s important to remember that, while thyroid function plays a role in both your energy levels and your ability to gain or lose weight, there are a lot of other factors that need to be considered.

Being tired all the time does not necessarily mean you have a thyroid condition, just as being cold does not automatically mean you have hypothyroidism. An inability to lose weight or gaining excessive weight does not mean your thyroid is abnormal. So while it’s appropriate to check in these situations, patients should realize there are a lot of other factors that could be going on, and a wider differential needs to be looked at when you’re having these concerns.

What Could High TSH Levels Mean?

Suffering from high TSH typically means one of two things, according to Dr. Winchell.

Hypothyroidism

The most common is an underactive thyroid gland, or hypothyroidism. If your thyroid is not producing enough thyroid stimulating hormone, your pituitary gland is going to release more TSH to try to get more T3 and T4 from the thyroid gland.

It’s a little tricky to wrap your head around, but having high TSH levels indicates low levels of T3 and T4.

High TSH Levels Symptoms

When a patient reports symptoms that include sudden weight gain, fatigue, low energy, irregular periods, or problems with sleep, it’s possible that this is because of high TSH. Because symptoms of having high TSH are also common symptoms for other conditions, the only way to know is to have a doctor provide a blood test to check your TSH levels.

Looking at cumulative symptoms over time is also valuable for helping reach a diagnosis.

Euthyroid Sick Syndrome

Another common diagnosis of high TSH comes from nonthyroidal illnesses, otherwise known as euthyroid sick syndrome. In this instance sick people, frequently those hospitalized in the ICU, are producing less T3 or T4 because of the illness that they’re suffering from.

What Could Low TSH Levels Mean?

Unlike high TSH, in which only a few conditions present themselves for relatively straightforward diagnoses, there are many reasons for low TSH. Low TSH means higher levels of T3 and T4 produced by the thyroid gland.

Graves’ Disease

The most common diagnosis is Graves’ disease, which triggers hyperthyroidism. Put simply, that means an overactive thyroid. In this autoimmune disorder, the thyroid becomes overactive because it is attacked by the body’s immune system.

Central Hypothyroidism

Another example is a syndrome called central hypothyroidism. In this case, your TSH may be low, but you’re considered to have hypothyroidism because of damage to the pituitary gland. In this example, the gland is not making enough TSH to adequately stimulate the thyroid gland to produce T3 and T4. It’s a bit of a challenge to diagnose, and there’s more work-up to figure it out.

Overmedication

Exogenous thyroid use could also lead to a diagnosis of low TSH. This can happen from either taking too much thyroid hormone replacement medication or from abusing thyroid hormone medication, which could lead to suppressed TSH.

Notes: This article was originally published February 1, 2022 and most recently updated July 19, 2022.

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TSH reference ranges should be used to safely guide thyroid hormone treatment in hypothyroid patients

CLINICAL THYROIDOLOGY FOR THE PUBLIC
A publication of the American Thyroid Association

Summaries for the Public from recent articles in Clinical Thyroidology

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HYPOTHYROIDISM
TSH reference ranges should be used to safely guide thyroid hormone treatment in hypothyroid patients

BACKGROUND
Hypothyroidism is a very common condition, also called an underactive thyroid. It can happen due to damage to the thyroid gland from inflammation or after certain treatments like surgery. If it is not treated it can lead to other illnesses such as heart disease and may even be life threatening. It also causes symptoms like fatigue and weight gain. Patients with hypothyroidism need to take thyroid hormone which is often a lifelong treatment. Current guidelines recommend that the dose of the thyroid hormone should be adjusted to resolve the symptoms and to keep the TSH level within the range of 0.4 – 4 mIU/L. Although this range is considered normal, we do not know for sure whether variations within this range result in different health outcomes.

The aim of this study was to explore whether risk of death or illnesses like heart disease and broken bones were more common at certain TSH levels in patients who were treated for hypothyroidism.

THE FULL ARTICLE TITLE
Thayakaran R et al 2019 Thyroid replacement therapy, thyroid stimulating hormone concentrations, and long term health outcomes in patients with hypothyroidism: longitudinal study. BMJ 366:l4892. PMID: 31481394.

SUMMARY OF THE STUDY
The study was done in United Kingdom using a database called The Health Improvement Network. Adult patients who were diagnosed with hypothyroidism between January 1, 1995 and December 31, 2017 were included in the study. The main outcomes were heart disease involving the blood vessels, heart failure, and stroke. Secondary outcomes were risk of death, irregular heart rhythm, and broken bones.

There were 162,369 patients in the 22-year study period. A total of 863,072 TSH measurements were analyzed. Risk of heart disease related to damage to blood vessels was higher when TSH level increased over 10 mIU/L. The risk of stroke was slightly less when TSH level was between 3-3.5 mIU/L and 4-10 mIU/L. Risk of death was higher when TSH level was lower than 0.1 mIU/L or especially above 10 mIU/L. Broken bones were more common at TSH levels above 10mIU/L, especially in women older than 65 years old.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that there was no evidence of negative outcomes when TSH levels were maintained in the recommended reference ranges in the guidelines (0. 4 – 4 mIU/L). Conversely, the risk of heart disease, stroke, broken bones and death was higher in hypothyroid patients with TSH levels outside the recommended reference range. Importantly, this range offers flexibility in treatment since patients may feel better at different TSH levels and the findings of this study support that this is a safe range.

— Ebru Sulanc, MD

ABBREVIATIONS & DEFINITIONS

TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also, the best screening test to determine if the thyroid is functioning normally.

Thyroid hormone therapy: patients with hypothyroidism are most often treated with Levothyroxine in order to return their thyroid hormone levels to normal. Replacement therapy means the goal is a TSH in the normal range and is the usual therapy. Suppressive therapy means that the goal is a TSH below the normal range and is used in thyroid cancer patients to prevent growth of any remaining cancer cells.

Hypothyroidism: a condition where the thyroid gland is underactive and doesn’t produce enough thyroid hormone. Treatment requires taking thyroid hormone pills.

Standards for the level of thysotropic hormone in the blood: the current state of the problem | Samsonova

One of the most controversial issues in modern thyroidology is the issue of TSH blood levels [4, 10]. The interest in this problem is understandable, since it is well known that the determination of the concentration of TSH in the blood is today considered a reference test in the laboratory assessment of the functional state of the thyroid gland, which allows timely detection of any violation of its function, including at the stage of asymptomatic hyper- and hypothyroxinemia. Thus, an increase in the content of TSH in the blood is the earliest laboratory sign of not only obvious, but also threatened thyroid pathology, especially thyroid insufficiency. In this regard, it is quite obvious that the verification of thyroid insufficiency largely depends on the standard upper limit of the TSH level in the blood. Currently, it is generally accepted that the concentration of TSH in the blood more than 4-5 mU / l indicates a decrease in thyroid function.

This article is a continuation of the discussion on the standards of the upper limit of normal for the level of TSH in the blood, open on the pages of both foreign and domestic journals.

The reason for the discussion was the latest recommendations of the US National Academy of Clinical Biochemistry to reduce the upper limit of normal for the level of TSH in the blood from 4 to 2.5 mU/l [8]. The basis for making such decisions was the results of the epidemiological study NHANES-111, which showed that during the examination of 13,344 people receiving adequate iodine prophylaxis, the level of TSH in the blood above 2.5 mU/l was determined in no more than 5% of cases [11]. At the same time, the study did not include those population groups that could potentially have deviations in the functional state of the thyroid gland [11]. Similar results were obtained in the European study SHIP-1 [18]. Thus, as a result of a survey of 1488 adults in Pomerania, no more than 5% had a TSH level in the blood above 2.12 mU/l [18].

It should be noted that not only after the publication of the recommendations of the US National Academy of Clinical Biochemistry, but long before that, articles began to appear in foreign literature, indicating that adult patients with a TSH blood level of 2–4 mU/l differ in a number of clinical signs and laboratory tests from a population with a blood TSH level of less than 2 mU/l. So, back in 1992, J. Staub et al. showed that a group of adults with an average TSH content in the blood of 3.0 ± 0.3 mU/l demonstrates a hyperergic TSH response to thyroliberin stimulation, which, as is known, indicates a decrease in the functional reserve of the thyroid gland [16]. According to the data of the Wickham study, in the group of people with a TSH level in the blood above 2 mU/l, overt hypothyroidism is more often diagnosed in the future [17]. Finally, in adults, this level of TSH is associated with an increased risk of hypercholesterolemia [7, 9, 14], endothelial dysfunction [12], and miscarriage [15]. According to our data, such a concentration of TSH in the blood of women of reproductive age is associated with hypoestrogenemia. Thus, every 8th (12.5%) woman of reproductive age, in whom, when assessing the functional state of the thyroid gland, the level of TSH in the blood was determined from 2 to 4 mU/l, had a reduced level of estrogen in the blood (the median of estradiol in this group of women was 167 pmol/l), while in all women with a TSH level in the blood below 2 mU/l, the content of estradiol was within the normal range (median of estradiol 235, 25 pmol/l, /> = 0.01) [5].

Moreover, in pregnant women (the most vulnerable part of the population in terms of the formation of pathological conditions associated with hypothyroxinemia), the level of TSH in the first trimester of gestation of more than 2 mU/l is currently recognized as an increased risk factor for the development of gestational hypothyroxinemia. So, according to our data, gestational hypothyroxinemia occurs in almost every 2nd pregnant woman with diffuse endemic goiter, who has a TSH level of 2 to 4 mU/l in the first trimester of gestation (/> = 0. 05) [2].

Thus, a similar blood TSH level in adults is associated with a known spectrum of pathological conditions, which today are a recognized consequence of chronic hypothyroxinemia.

At the same time, it should be emphasized that all the accumulated knowledge and understanding of the clinical and prognostic significance of the concentration of TSH in the blood more than 2, but less than 4 mU/l was obtained on the basis of a survey of the adult population. The following data allow us to form an opinion on the significance, legitimacy and expediency of isolating this particular range of TSH levels in the blood and in pediatric practice. Thus, according to the results of a study by D.E. Shilin (2002), children and adolescents (n = 114) with a basal TSH level in the blood above 2 mU/l (average 2.57 ± 0.06 mU/l) differ from children and adolescents (n = 475) with a basal TSH level below 2 mU/l (average 1.19± 0.02 mU/l) [6].

In 94.1% of children (p < 0.05) of this group, a hyperergic TSH response to thyroliberin stimulation is observed, which indicates a reduced functional reserve of the thyroid gland [6]. According to the same author, such children and adolescents have significantly (/> = 0.03) higher concentrations of atherogenic lipid fractions, and adolescent girls with a similar level of TSH in the blood show signs of age-related immaturity of the uterus and gonads (p = 0.01) [6]. In addition, such girls are prone to polymenorrhea (menstruation lasts an average of 5.5 ± 0.3 days versus 4.7 ± 0.1 days in the group of girls with TSH levels in the blood below 2 mU/l; p = 0.01) and a lower level of estradiol in the blood (mean estradiol content 162 ± 23 pmol/l versus 239 ± 22 pmol/l in the group of girls with a TSH concentration in the blood of less than 2 mU/l; p = 0.05) [6].

According to our data, it is adolescent girls with TSH levels in the blood above 2 but below 4 mU/l that are most vulnerable in terms of the formation of functional disorders of the reproductive system. So, according to the results of our research, every 2nd (54%) girl with a similar level of TSH in the blood has menstrual dysfunction of the type of opsomenorrhea (while only 28% of girls with a TSH level below 2 mU/l, Р = 0. 032) [1].

So, in our opinion, today there are enough arguments in favor of the fact that the level of TSH in the blood from 2 to 4 mU/l in children also reflects the earliest in terms of onset and the mildest in severity thyroid insufficiency.

Obviously, thyroid insufficiency in iodine-deficient regions has its own evolution. In our opinion, the evolution of thyroid insufficiency can be represented as follows: 1) a normal level of free thyroxin and a TSH level of 2 to 4 mU/l, there are no clinical signs of hypothyroidism; 2) normal level of free thyroxine and TSH level above 4-5 mU/l, there are no clinical symptoms of hypothyroidism; 3) a reduced level of free thyroxine and a TSH level above 4-5 mU/l in combination with clinical signs of hypothyroidism. The last two stages of thyroid insufficiency are well known and are classified as subclinical and overt hypothyroidism, respectively.

At the same time, today there is no single generally accepted term that characterizes the level of TSH from 2 to 4 mU/l. This is understandable, since terminology issues are always the most difficult. In the English literature, the TSH level in the traditionally normal range, but above 2 mU/L, is denoted by the following terms: “high-normal TSH” [14], “very mild thyroid failure” [15], “a lessened thyroid reserve” [15], “mildest form of subclinical hypothyroidism” [16]. We propose to use the term “minimal thyroid insufficiency” to designate the condition, which is reflected in the level of TSH from 2 to 4 mU/l. In our opinion, it is he who most accurately characterizes the earliest in terms of onset and the mildest in severity thyroid insufficiency.

At the same time, at a given level of TSH, the functionality of the thyroid gland should be assessed depending on its size. So, in persons without goiter, a slight increase in the level of TSH (2-4 mU / l) only indicates that, with normal sizes, the thyroid gland is not able to provide adequate production of thyroid hormones. In this group of people, a similar level of TSH reflects the readiness to turn on compensatory mechanisms leading to an increase in the size of the thyroid gland and to the normalization of the level of thyroid hormones. Thus, in persons with normal thyroid gland sizes, this condition cannot yet be classified as a pathology, but should be considered as a borderline condition.

In patients with long-term goiter, this level of TSH indicates that the increase in the size of the thyroid gland did not lead to the elimination of hypothyroxinemia and, therefore, the required level of thyroid hormones was not achieved. Most likely, in this case, there was a decrease in the compensatory and functional reserves of the thyroid gland due to a mild genetic defect in morpho- or hormonogenesis. Even with mild congenital insufficiency of the thyroid gland in conditions of insufficient iodine intake, the formation of goiter will not lead to the normalization of thyroid status, i.e., to the elimination of hypothyroxinemia and, consequently, the risk of iodine deficiency diseases.

We are deeply convinced that the use of the term “minimal thyroid insufficiency” in the context in which it is presented in the article will not only not mislead readers, but, on the contrary, will help to understand the essence of the problem and present the evolution of thyroid insufficiency in iodine-deficient regions.

It should be noted that another, no less, and perhaps more important issue of this discussion is whether people with a TSH blood level of 2 to 4 mU / l need therapy. Foreign and domestic authors consider the danger of expanding indications for verification of hypothyroidism and treatment of such a patient with levothyroxine preparations as a serious argument against the recognition of new standards for THG in the blood [4, 10].

In our opinion, the TSH level in the range from 2 to 4 mU/l only indicates that in the region of iodine deficiency the thyroid gland is able to maintain an ideal euthyroid state only if there is an adequate supply of iodine. It is quite obvious that in the absence of adequate iodine prophylaxis in regions with even moderate and / or mild iodine deficiency (i.e., in most of the territory of Russia), it is this degree of thyroid insufficiency that will continue to occur frequently and determine the formation of medically and socially significant iodine deficiency states. Hence the conclusion that the vast majority of people living in these conditions and having a similar level of TSH in the blood need only adequate iodine prophylaxis. Adequate iodine prophylaxis in most of them is able to maintain an ideal euthyroid state for many years of life.

The exception is 2 groups of people. First of all, these are pregnant women with a TSH level in the first trimester of gestation above 2 mU/l, i.e., those with a risk factor for the development of gestational hypothyroxinemia [2]. Taking into account the exceptional role of the normal level of maternal thyroxine for the formation and maturation of the central nervous system of the unborn child and the need for rapid and effective correction of gestational hypothyroxinemia, today no one doubts and objects that pregnant women with a similar level of TSH need treatment with levothyroxine preparations. In addition, it is required to prescribe levothyroxine preparations to persons exposed to other (except for iodine deficiency) strimogenic environmental factors or having more pronounced genetically determined defects in morpho- or hormone genesis of the thyroid gland. It should be emphasized that these are extremely rare cases.

When deciding on the TSH level standards, the modern double standards used to assess the functional state of the thyroid gland in untreated individuals and in patients receiving levothyroxine replacement therapy are somewhat surprising [3, 13]. In this regard, another strong argument in favor of narrowing the normal range for the level of TSH in the blood is that the vast majority of researchers have recognized and do not raise objections to TSH levels ranging from 0.5 to 2 mU/l as reflecting the euthyroid state of the thyroid gland in patients receiving replacement therapy with levothyroxine drugs [3, 13].

So, the above data convince us that today there are more than enough arguments in favor of recognizing the fact that (both in adults and in children) the TSH level from 2 to 4 mU/l reflects the earliest in terms of onset and the mildest in severity thyroid insufficiency, namely, minimal thyroid insufficiency.

Narrowing the normal range of TSH levels in the blood from 0.5 to 2-2.5 mU/l and the speedy implementation of these standards in healthcare practice is a necessary condition for optimizing the early diagnosis, prevention, treatment of hypothyroxinemia and, consequently, the elimination of iodine deficiency conditions in Russia.

1. Bukanova SV Thyroid status and functional state of the reproductive system in children and adolescents living in an industrial metropolis with moderate to mild iodine deficiency: Authors. dis…. cand. honey. Sciences. -M., 2004.

2. Ivakhnenko VN Tirsoid, neuropsychiatric and somatic status of children born to mothers with goiter: Abstract of the thesis. dis…. cand. honey. Sciences. Moscow, 2005.

3. E. P. Kasatkina, M. I. Martynova, V. A. Peterkova, et al., Klin. thyroidol. – 2003. – V. 1, No. 1. – S. 26-27.

4. V. V. Fadeev // Klin. thyroidol. – 2004. – V. 2, No. 3. – S. 5-9.

5. Chubarova D.Yu. Reproductive health of women in the region of mild goiter endemia: Abstract of the thesis. dis…. cand. honey. Sciences. – M., 2006.

6. Shilin D. E. //Laboratory. – 2002. – No. 3. – S. 22-26.

7. Bakker S. J. L., Ter Matten J. C, Popp-Sni/ders C. et al. // J. Clin. Endocrinol. Metab. – 2001. – Vol. 86. – P. 1206-1211.

8. Baloch Z, Carayon P., Conte-Devolx B. et al. // thyroid. – 2003. Vol. 13.-P. 3-126.

9. Bindels A. J., Weslendorp R. C, Frolich M. et al. // J. Clin. Endocrinol. – 1999. – Vol. 50.-P. 217-220.

10. Brabant G., Beek-Peccoz P., Jarzab B. et al. // EUR. J. Endocrinol. – 2006. – Vol. 154. – P. 633-637.

11. Hollowell J. C, Siaehling N. W, Flanders W. D. et al. // J. Clin. Endocrinol. Metab. – 2002. – Vol. 87. – P. 489-499

12. Lekakis J, Paramlchael C, Alevizaki M. et al. // thyroid. – 1997. – Vol. 7. – P. 411-414.

13. McDermott M. T., Ridgway C // i. Clin. Endocrinol. Metab. -2001. – Vol. 86.-P. 585-590.

14. Michalopoulou C, Alevizaki M., Piperingos C. et al. // EUR. J. Endocrinol. – 199S. – Vol. 138. – P. 141-145.

15. Prummel M. F, Wienlnga W. M. // Eur. J. Endocrinol. – 2004. – Vol. 150. – P. 751-755.

16. Staub J. J., Althaus B. V., Engler H. et al. // Am. J. Med. – 1992. – Vol. 92, No. 6. – P. 632-642.

17. Vanderpump M. P., Tunbridge W. M. C, French J. M. et al. // J. Clin. Endocrinol. – 1995. – Vol. 43. – P. 55-68.

18. Volzke H., Ludemann J., Robinson D. M. et al. // thyroid. – 2003. – Vol. 13. – P. 803-810.

TSH: function, norms and deviations

Life processes in the human body are regulated by the nervous and endocrine systems. An important function in this is assigned to the hypothalamic-pituitary complex. It consists of parts of the brain that regulate the vegetative functions of the body. They produce a number of hormones that control the activity of the endocrine glands. In particular, TSH coordinates the work of the thyroid gland. It is produced by the anterior pituitary gland. In turn, thyroid hormones also perform a number of important functions. They support the metabolism of various substances, regulate the functioning of organs, systems and tissues. In children, they take part in the correct physical and mental development of the body.

The effect of TSH on the vital activity of the body

The main function of thyroid-stimulating hormone is the mutual regulation of the synthesis of the thyroid hormones T3 and T4. If T3 and T4 free is lowered, TSH stimulates their production, and they, on the contrary, are able to inhibit the synthesis of thyroid-stimulating hormone. This process is triggered in the event of an increase in the concentration of T3 and T4. Thus, the correct hormonal balance in the body of a healthy person is maintained.
In addition, TSH regulates the production of a number of important substances, including proteins and lipids. The hormone affects the thyroid gland in several ways: vascularization, regulation of iodine absorption, increased blood flow, stimulation of hormone synthesis, and acceleration of gland growth.

TSH levels and deviations

Violation of the level of TSH is possible in both women and men, but normal levels differ depending on gender. An analysis for TSH is prescribed if the doctor suspects a thyroid disease.
Reference values ​​in adults: from 0.4-0.5 mIU / l to 4.2-5 mIU / l. For children, normal rates are determined according to age. During childbearing, the allowable range of thyroid-stimulating hormone concentration depends on the gestational age. In men, the concentration of the hormone usually does not exceed 3.5 mIU / l. A variety of factors can affect TSH levels. For example, during prolonged exposure to cold, TSH is elevated, as the body increases its metabolism by 20% to adapt to extreme conditions.
Self-assessment of the results of laboratory analysis does not lead to anything good. A person comes up with a non-existent diagnosis for himself, begins to worry about this, exacerbating the situation. Only a doctor can correctly interpret the results of the analysis. At the same time, he takes into account the age and gender of the person, the presence of concomitant diseases, the clinical picture and other points.

When to check the TSH level

An analysis of the thyroid gland is prescribed in case of suspicion of its dysfunction. The doctor may recommend taking it if you have symptoms such as constant weakness, depression, sleep disturbances, decreased libido, baldness, visually noticeable enlargement of the thyroid gland, and so on. If a thyroid disease has already been identified (for example, a toxic goiter is diagnosed), regular studies are prescribed to monitor the patient’s condition and evaluate the effectiveness of therapy.
After the age of 40, the risk of problems in the thyroid gland increases. The disease can be asymptomatic for a long time. Therefore, all people over 40 are recommended to regularly take such a blood test. The thyroid gland responds well to therapeutic treatment only in the early stages of the pathological process, so it is important to identify the disease as early as possible.