Thyroid stimulating hormone (TSH) is a peptide hormone that is responsible for regulating the levels of thyroid hormones in the body. TSH is secreted by the pituitary gland. This hormone stimulates the thyroid gland to secrete the hormones T3 and T4. The normal levels of TSH in the blood is somewhere between 0.4 - 5.0 mIU/l. However, there are certain conditions where the levels of these hormones may go beyond 5.0 mIU/l.
Main Causes of Elevated TSH
Any kind of alteration in the levels of TSH may indicate an underlying thyroid problem. Elevated TSH levels signify an under-active thyroid gland. There may also be other causes, such as:
This is a benign tumor of the pituitary gland, which accounts for around 10% of all the intracranial neoplasms. These lesions often remain undiagnosed, until they lead to systemic symptoms, like an imbalance in certain hormone levels. This type of adenoma that will lead to changes in the TSH hormone is quite rare, and is known as thyrotrophic adenoma. It usually doesn't cause any symptoms immediately, although there may be elevated TSH symptoms which mimic the symptoms of hyperthyroidism.
Thyroid Hormone Resistance
This is a rare syndrome, where the thyroid hormone levels are elevated, but still the levels of TSH are not suppressed. The most common cause of this condition is a genetic mutation of the thyroid hormone receptor. The symptoms that a person may present are highly variable, and at times the person may not show any symptoms at all. At other times, the person may exhibit signs of goiter and tachycardia.
Another condition where elevated TSH levels are seen in children is congenital hypothyroidism, which is also known as cretinism. In this condition, the thyroid hormone levels are low right from birth. So in an attempt to boost the levels of T3 and T4, the pituitary gland secretes more of TSH, leading to a rise in TSH levels in the blood. If left untreated, the infant can suffer from growth failure and mental retardation.
Hypothyroidism is a condition, where there are low levels of T3 and T4. In adults, this may occur due to conditions like iodine deficiency. Hypothyroidism may even occur as a result of an autosomal recessive genetic disorder. Due to lowered functioning of the thyroid gland, the pituitary gland is stimulated to secrete excess of TSH hormone, which then reflects in the blood. This is especially seen during pregnancy.
It is an autoimmune condition, where the thyroid gland cells get attacked by antibodies of the host cell. Due to progressive destruction of the thyroid gland, there is lowered functioning of the thyroid cells, leading to signs and symptoms of an under-active thyroid. There are intermittent bouts of hyperthyroidism as well. Symptoms include weight gain, depression, mania, increased sensitivity to cold, fatigue, bradycardia, constipation, muscle weakness, cramps, etc.
The treatment for elevated TSH levels will depend on the exact underlying cause. In case of adenoma, the treatment will depend on the size and rate of progression of the cancer. In case of an autoimmune disease like Hashimoto's thyroiditis, one can take immunosuppressive drugs to mitigate the symptoms. Elevated TSH levels are an important indicator when it comes to thyroid diseases and disorders. If you are showing symptoms of hypothyroidism, then it is best that you get the TSH blood test done, so that the doctor can diagnose and treat your condition at the earliest.