Why is TSH high?

Thyroid stimulating hormone is an important homeostatic hormone and plays a very important role in the safety of the body. Therefore, people must pay attention to protecting the safety of the thyroid gland in their lives. However, the safety of the thyroid gland is difficult to ensure in certain circumstances. Once a pathological reaction occurs, the secretion of thyroid stimulating hormone will be high. Let's take a look at the explanation of why thyroid stimulating hormone is high.

The so-called thyroid-stimulating hormone is a growth hormone in the human body. It plays an indispensable role in the human body, but both high and low values ​​of thyroid-stimulating hormone will have a great impact on people.

1. Thyroid-stimulating hormone is a hormone secreted by the pituitary gland that promotes the growth and function of the thyroid gland. Human TSH is a glycoprotein containing 211 amino acids, with carbohydrates accounting for approximately 15% of the entire molecule. The entire molecule consists of two peptide chains - the α chain and the β chain. TSH comprehensively promotes the function of the thyroid gland. The earlier one is to promote the release of thyroid hormones, and the later one is to promote the synthesis of T4 and T3, including strengthening the activity of iodine pump, enhancing the activity of peroxidase, promoting the synthesis of thyroglobulin and tyrosine iodination, etc.

2. Thyroid-stimulating hormone causes cells to proliferate in a tall columnar shape, thereby enlarging the gland. The pituitary gland secretes TSH, which is on the one hand influenced by the thyrotropin-releasing hormone (TRH) secreted by the hypothalamus, and on the other hand influenced by the feedback inhibitory effects of T3 and T4. The two antagonize each other and form the hypothalamus-pituitary-thyroid axis. Under normal circumstances, the amount of TRH secreted by the hypothalamus determines the level of feedback regulation of the adenohypophysis-thyroid axis.

3. If TRH is secreted more, the set point of T3 and T4 levels in the blood will be high. When T3 and T4 in the blood exceed this set level, it will feedback inhibit the secretion of TSH by the pituitary gland and reduce the sensitivity of the pituitary gland to TRH, thereby keeping the levels of T3 and T4 in the blood relatively constant. External stimuli such as sudden cold promote the release of TRH in the hypothalamus through the central nervous system, and then through the adenohypophysis-thyroid axis, increase the levels of T3 and T4 in the blood. TSH secretion has a circadian rhythm, with the highest level at 2 to 4 in the morning, then gradually decreasing to the lowest level at 6 to 8 in the afternoon.