What is TSH?

TSH is the abbreviation of the initials of the words Thyroid Stimulating Hormone. TSH is secreted from the pituitary gland in the brain and ensures the production of thyroid hormones (T4 and T3) from the thyroid gland. A certain level of TSH is essential for normal secretion of thyroid hormones from the thyroid gland.

How to Determine Increased TSH?

TSH elevation is determined by blood tests. Normal values ​​of TSH are generally accepted as 0.35-4.5 mIU/L. Although normal ranges may differ from laboratory to laboratory, it is generally considered high if TSH is above 4.5 mIU/L. However, the evaluation of TSH elevation in various situations differs. For example, it is aimed to have a lower TSH in pregnant women (below 2.5 mIU/L in the first trimester, less than 3 mIU/L after the third month). On the other hand, age is also one of the factors determining TSH limits, and TSH can be considered normal up to 7.5 mIU/L if the patient has no complaints over the age of 80.

What are the Causes of High TSH?

Underactive thyroid gland (hypothyroidism) is the most important cause of high TSH. In other words, high TSH is an indication that the thyroid gland is underactive, that is, it produces less hormones. In fact, when the thyroid is underactive, the brain raises TSH in order to correct this situation and raise the thyroid hormone level (to bring it back to normal).

All the reasons that may cause the thyroid gland to work less can cause high TSH. These include Hashimoto's thyroiditis, underactivity of the thyroid gland after surgery or atomic therapy, iodine deficiency and various medications. Very rarely, tumors in the pituitary gland and conditions characterized by thyroid hormone resistance may cause elevated TSH in some patients.

What is the Relationship Between High TSH and Thyroid Failure?

One of the main conditions that determine thyroid failure with high TSH is the level of hormones called T4 and T3 secreted from the thyroid. Although TSH is elevated initially, the level of thyroid hormones may not have decreased yet, that is, TSH may be high when thyroid hormones are normal. This condition is called mild thyroid insufficiency (subclinical hypothyroidism). At this point, clinical signs and symptoms may be very mild or no signs and symptoms may be observed. Over time, thyroid hormone levels may begin to drop in the blood, and the signs and symptoms of thyroid failure become evident.

What Complaints and Symptoms Can High TSH Cause?

If thyroid hormones are normal in the blood, no complaints may be seen. However, some people may show signs and symptoms of thyroid failure, even if thyroid hormones do not decrease in the case of high TSH.

Since thyroid hormones regulate the metabolism of many systems in the body, signs and symptoms related to many systems can be seen. The most common complaints in these people are weakness, fatigue, forgetfulness, depression, easy cold, dry skin, hair loss, weight gain and inability to lose weight, constipation, swelling around the eyes, high cholesterol, hoarseness, sexual reluctance, menstrual irregularity and infertility in women. In case of high TSH and thyroid insufficiency, one or more of these complaints may be present, not all of them. On the other hand, the presence of these complaints does not necessarily indicate thyroid disease, but may be due to other systemic diseases.

What Should I Do in Case of High TSH?

If your TSH level is found to be high, consult an endocrinology and metabolic diseases specialist. Your doctor will first investigate the causes of high TSH. In addition to nutritional recommendations, he will start thyroid hormone treatment when he deems it necessary and will follow you at regular intervals to keep your thyroid hormone values ​​at the required levels.

Prof Dr Mahmut Muzaffer Ilhan

Endocrinology and Metabolism Diseases