Normal Thyroid Stimulating Hormone (TSH) Levels – by Age

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What is the thyroid hormone?

The thyroid gland is a kind of butterfly-shaped gland in front of the neck, wrapping around the windpipe. Throughout your body, glands produce and release chemicals that assist your body in performing certain functions. Your thyroid gland develops and secretes hormones that are involved in various functions throughout your body. It also helps to regulate your weight, body temperature, muscular strength and even your mood.

What is the thyroid hormone?

TSH is a thyroid-stimulating hormone. It is secreted in the pituitary gland of the brain. When your thyroid levels are low, the pituitary gland produces a higher level of TSH. TSH secretion by the pituitary gland is reduced when thyroid levels are high. TSH readings that are too high or too low might suggest that your thyroid is not functioning properly. Thyroid illness is classified into numerous kinds, including hyperthyroidism, hypothyroidism, thyroiditis and Hashimoto’s thyroiditis.

What does TSH levels indicate?

The amount of thyroid hormone in the body has an inverse relationship with TSH levels. 

Abnormally high TSH levels indicate that your thyroid is not functioning properly. When the thyroid hormone levels are low, the pituitary gland responds by producing more TSH to balance the levels. This is termed hypothyroidism.

Low TSH levels indicate that the body is producing excess thyroid hormones. As a result, the pituitary gland reduces the amount of TSH it produces to control thyroid activity. It’s known as hyperthyroidism.

Thyroid function is properly measured using serum thyroid-stimulating hormone (TSH) and thyrotropin levels. The thyroid hormone exists in the main forms – thyroxine (T4) and triiodothyronine (T3). Thyroid disorders can occur at any age and are more prevalent in women.

Thyroid diseases may affect anybody, including men, women, newborns, adolescents and the elderly. It might be present at birth (usually hypothyroidism) or develop as you become older (often after menopause in women).

If your doctor believes you have a thyroid problem, you may request one or more thyroid function panel blood tests. These tests assess thyroid hormone levels in the blood and can help you determine  how well your thyroid gland is functioning.

The thyroid tests include:

  1. Thyroid-stimulating hormone (TSH)
  2. Free T4 (thyroxine)
  3. T3 (triiodothyronine)

What does a normal TSH level look like?

TSH levels are monitored in ranges. TSH levels should be within the normal reference range of 0.5 to 5.0 milli-international units per litre (mIU/L) of blood. A TSH level in this range shows that the thyroid gland is working properly.

Doctors, however, disagree on the precise TSH range of a normal-functioning thyroid gland. Some clinicians consider a TSH level of 4.5 mIU/L to be an indicator of an underactive thyroid.

Before diagnosing you with thyroid disease, your doctor will take into account not just your TSH level but also any indications or symptoms you’re experiencing, such as an enlarged thyroid gland.

TSH levels for women: During menstruation, childbirth and menopause, women are at a considerable risk of acquiring elevated TSH levels.

TSH levels for men: TSH levels, both high and low, can have an impact on fertility. Men with hypothyroidism or hyperthyroidism had less normal shaped sperm.

And if they have high TSH, men are more likely than women to experience issues like irregular genital development. To balance TSH, men may need to take thyroid hormone replacement medication.

TSH levels during Pregnancy

It is vital to keep an eye on the TSH levels throughout pregnancy. High TSH levels and hypothyroidism may affect pregnancy and can increase miscarriage risk.

Due to this, certain pregnant women may be given levothyroxine, methimazole or propylthiouracil (PTU) to assist in managing TSH and thyroid hormone levels, particularly if they have hypo- or hyperthyroidism.

A doctor may advise raising the dose by around 30% to 50% if the woman is already taking this medicine for abnormal thyroid hormone levels during pregnancy.

Reduced risk of miscarriage can result from effective treatment of high TSH and hypothyroidism during pregnancy. Managing TSH levels helps treat several issues. These include, 

Thyroid hormones and the process of ageing

Ageing has a significant impact on the entire endocrine system (a complex network of glands and organs). Similarly, ageing has a consistent influence on the thyroid gland. It is important to note that the symptoms of thyroid illness in the elderly are remarkably equivalent to those of normal ageing. As a result, expanding information on changes in thyroid function that may be detected throughout ageing looks to be highly essential and poses a challenge for thyroid researchers, given that some specific thyroid dysfunctions may lead to an  increased life span.

What is the significance of a low TSH level?

A TSH level less than 0.5 mIU/L may indicate that your thyroid gland is hyperactive. This is hyperthyroidism, which can induce unexplained weight loss, heat sensitivity, increased hunger and protruding eyes.

Graves’ disease, an autoimmune ailment in which your body’s immune system erroneously targets the thyroid gland, is one of the most prevalent causes of hyperthyroidism. Goitre, or the usage of certain drugs, can also induce hyperthyroidism. Other causes are thyroid nodules, Thyroiditis and consuming excess iodine.

Low TSH levels generate the following symptoms:

  • Palpitations
  • Feeling shaky and nervous
  • Increased appetite
  • Weight loss
  • Menstrual changes
  • Sleep issues
  • Vision problems
  • Muscle weakness
  • Hair loss and change in hair texture

What does a high TSH level mean?


A TSH level above 5.0 mIU/L indicates an underactive thyroid gland or hypothyroidism.

A low thyroxine level and a high TSH level imply an underactive thyroid. This is because your pituitary gland creates more TSH to urge your thyroid gland to make more thyroid hormones.

High TSH levels generate the following symptoms:

  • Dry skin
  • Insufficiency in cold
  • Constipation
  • Difficulty concentrating or focusing (“brain fog”)
  • Weight gain
  • Hair thinning
  • Irregular menstrual cycles
  • Slow heart rate
  • Brittle nails
  • Muscle cramps, weakness and joint pain

Hypothyroidism and Pregnancy

Some women suffer from a thyroid disorder that develops before pregnancy (also called a pre-existing condition). Others may experience their first thyroid difficulties during pregnancy or shortly after giving birth.

Thyroid disease may not create any complications during pregnancy if treated. Untreated thyroid issues, on the other hand, might pose complications for you (such as preeclampsia,  premature birth and having a baby with a low weight at birth) and your kid throughout pregnancy and after birth. The infant relies on the mother for thyroid hormones throughout the first few months of pregnancy. These hormones are essential for the baby’s appropriate brain development and growth. Hypothyroidism in the mother might have long-term consequences for the foetus.

How should I get ready for a test for thyroid-stimulating hormone?

  • Amiodarone 

Even in the absence of hyperthyroidism or hypothyroidism, amiodarone can have a number of consequences on the results of thyroid function tests. Thyroxine, reverse triiodothyronine, and thyroid-stimulating hormone serum levels may rise, whereas serum triiodothyronine levels may fall as a result.

  • Dopamine

 Dopamine receptors on the surface of anterior pituitary cells may be stimulated by the neurotransmitter, leading to a fast drop in TSH secretion. The amount of this hormone in the body is determined by a thyroid-stimulating hormone test. The test assists in determining whether the thyroid is present or not.

  • Lithium 

 The thyroid concentrates lithium, which prevents the thyroid from absorbing iodine. Additionally, it affects the structure of thyroglobulin, which prevents the release of thyroid hormone, and inhibits iodotyrosine coupling.

  • Prednisone 

Prednisone was given orally at a dose of a minimum of 20 mg every day for nine days. This caused a significant drop in mean serum TSH levels but had no noticeable effects on serum T4, T3 or thyroxine-binding globulin levels (TBG).

  • Potassium iodide 

In severe cases of thyrotoxicosis, potassium iodide (KI) is effective in treating thyroid hormone-related diseases by affecting thyroid hormone synthesis. Additionally, Potassium Iodide (KI) is a salt that can shield the thyroid from radiation exposure.

  • Biotin 

Most frequently, taking biotin can cause falsely high T4 and T3 levels and falsely low TSH readings, which can lead to either a mistaken diagnosis of hyperthyroidism or a misleading conclusion that the thyroid hormone dose is too high.

How is a thyroid-stimulating hormone test performed? 

Here’s how the thyroid stimulating hormone test is performed.

Thyroid stimulating hormone (TSH) test procedure

Clean the area with an antiseptic

Before performing the test, the health care practitioner should gently clean the area with some antiseptic or any sterilising solution. This relaxes the area and steadies the muscle for examination.

Tie an elastic band around your arm

A tight elastic band is rounded around the area of your arms. This causes the veins to swell with the blood.

Inserting a needle

blood sample

With the use of a tiny hollow needle, a small portion of the blood is taken out. The thyroid gland is located in the front of your neck.

Draw enough blood 

After the needle insertion into the skin, blood is drawn out of the veins, which is then taken to the laboratory for the test.

Treating abnormal TSH levels

If the TSH levels are abnormal, one or more of the following treatments is advisable.

Hypothyroidism (high TSH) 

  • Prescription medications, such as levothyroxine.
  • Taking foods like fibre, soy, iron, or calcium in less amounts as they interfere with the absorption of levothyroxine.

Hyperthyroidism (low TSH) 

  • Radioactive iodine is taken orally.
  • Methimazole or propylthiouracil is advisable to prevent the thyroid from producing too much thyroid hormone.
  • Removal of the thyroid gland if treatments are ineffective or cause harm to the health.

When to see a doctor? 

Ask your primary care physician if you should be examined if you experience one or more of thyroid symptoms or if you have a family history of thyroid malfunction.

To examine the function of your thyroid, doctors may request one or more blood tests. TSH, T4, T3, and thyroid antibody tests are among the possible examinations. Your thyroid function is examined via thyroid blood tests. A blood sample will be collected from the patient, which will then be sent to a lab for analysis.

In conclusion

If your TSH levels are over the usual range, consult with your doctor to determine the reasons. Make sure to disclose any health issues you are having. Also, provide your doctor with a list of any medications, vitamins, minerals, herbs and other dietary supplements you use. Some of these items may interfere with thyroid function and result in an abnormal test result.

It is impossible to find a TSH level that is ideal for everyone. This is because TSH levels vary based on a variety of factors, including your age, thyroid status and maybe even how well you sleep at night or when you last ate.

TSH blood testing is used by doctors to diagnose thyroid conditions.

The majority of the time, thyroid issues can be treated with medication, surgery, or a combination of the two. TSH testing will probably be necessary on a regular basis for those with thyroid disorders to make sure their symptoms are kept under control.


 What is the normal TSH level for age? 

TSH levels are monitored in ranges. TSH levels should be within the normal reference range of 0.5 to 5.0 milli-international units per litre (mIU/L) of blood. A TSH level in this range shows that the thyroid gland works correctly.

What causes TSH to rise?

The improper functioning of the thyroid gland triggers the Thyroid Stimulating Hormone (TSH) to rise.

 Can I lower my TSH naturally? 

By controlling the thyroid gland’s activity, a diet high in protein helps to improve the thyroid hormone synthesis that has been lowered. Protein-rich foods, including nuts, green vegetables, eggs, meat, and legumes, may help reduce the symptoms of hypothyroidism.

 What foods increase TSH? 

By controlling the thyroid gland’s activity, a diet high in protein helps to improve the thyroid hormone synthesis that has been lowered. Protein-rich foods, including nuts, green vegetables, eggs, meat, and legumes, may help reduce the symptoms of hypothyroidism.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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