Thyroid Stimulating Hormone, as the name suggests, stimulates the thyroid gland and is thus responsible for the release of thyroid hormones T3 and T4. The pituitary gland regulates the function of the thyroid gland by releasing the hormone TSH as per requirement. If the thyroid becomes hyperactive, TSH production is restricted, whereas if it becomes underactive, high amounts of TSH are released to stimulate the gland. Thus, elevated TSH levels indicate a severely underactive thyroid. But, there are certain other factors responsible for this condition. The following transitions shed light on the possible causes and symptoms observed.
Causes of Increased TSH Levels
► 0.3 - 3.0 mIU/L is considered as the normal level of TSH in blood. This is as per the revised TSH normal value furnished by the American Association of Clinical Endocrinologists.
► The association had revised the value in 2003; however, many labs and doctors still consider 0.4 to 6 or 0.4 to 4.0 mIU/L as the normal TSH level.
► So, while interpreting the TSH test reports, you should first check the normal value of reference and then conclude about the condition accordingly.
► Though 3.0 is the upper limit of the normal value, any value above 2.0 indicates slow functioning of the thyroid.
► If a person shows a TSH value higher than 4.0 mIU/L, then the condition is considered to be extremely serious. Abnormally high levels of TSH are reflective of a severely underactive thyroid. Thus, an underactive thyroid is one of the main causes of exceedingly high TSH levels.
► Iodine deficiency or an autosomal recessive disease can result in an underactive thyroid leading to hypothyroidism. Even in pregnancy, women may suffer from high TSH problems.
Thyroid Hormone Resistance
► This kind of resistance is rarely seen, but it is one of the causes. Sometimes, despite the release of high thyroid hormone levels, the levels of TSH are not suppressed.
► A genetic mutation of the thyroid hormone receptor can lead to such a situation. Some people do not exhibit any symptoms of thyroid hormone resistance, while a few others may exhibit. However, the symptoms usually vary from person to person.
► Sometimes, a benign or cancerous tumor of the pituitary gland leads to an imbalance of TSH levels. Thyrotrophic adenoma affects the TSH levels seriously.
► This is a rare type of adenoma in which the symptoms are not seen immediately. The patient may experience symptoms of hyperthyroidism.
► Unfortunately, some children are born with hypothyroidism, and the condition is known as cretinism.
► High TSH is often noticed in such children. If left untreated, the disorder can result in mental retardation and poor physical growth.
► It is an autoimmune disorder in which the cells of the thyroid gland are destroyed by the antibodies of the host cell. Thus, progressive destruction of the thyroid gland results in hypothyroidism.
► Sometimes, symptoms of hyperthyroidism may also be noticed. Weak muscles, muscle cramps, weight gain, and slow pulse rate are some of the indicants of Hashimoto's thyroiditis.
Affected Function of the Hypothalamus
► The hypothalamus releases the hormone 'thyrotropin' and controls the function of the anterior pituitary gland. Thus, it also plays an important role in the release of TSH.
► Another hormone 'somatostatin', released by the hypothalamus works as the antagonist of 'thyrotropin'. Therefore, an imbalance of somatostatin and thyrotropin can also result in abnormal TSH levels in the blood.
Symptoms of High TSH Levels
- Tremendous weakness and constant fatigue
- Hair loss and thinning of hair
- Difficulty in waking up
- Difficulty in losing or gaining weight
- Dry and rough hair
- Dry and dull skin
- Intolerance to cold
- Bradycardia (slow pulse rate)
- A pale or yellowish skin
- Brittle nails
- Increased irritability and depression
- Severe mood swings
- Irregular periods and abnormal menstruation
- Hypotonia (a muscle disorder)
- Reduced sex drive
- Loss of memory
- Herniated belly button
- Hoarse crying
- Affected physical growth and short stature
- Weak muscles
- Enlarged thyroid and swollen neck
- Cold hands and feet (low body temperature)
- Lack of appetite
- Swollen face
- Low pulse rate
- Frequent choking
- Enlarged and swollen tongue
- Delayed development of permanent teeth
- Slow and poor mental development
A simple blood test helps in determining the levels of TSH. Knowing the exact cause of high or low TSH levels helps in determining the right treatment. Symptoms of hypothyroidism and hyperthyroidism need prompt medical attention. Consult your doctor immediately if you notice any of the above symptoms.
Disclaimer: This HealthHearty article is for informative purposes only and should not be used as a replacement for expert medical advice.