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As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland. The hypothalamus senses low circulating levels of thyroid hormone (Triiodothyronine (T3) and Thyroxine (T4)) and responds by releasing thyrotropin-releasing hormone (TRH). The TRH stimulates the anterior pituitary to produce thyroid-stimulating ...
Diagram of the hypothalamic–pituitary–thyroid axis. The hypothalamus secretes TRH (green), which stimulates the pituitary gland to produce TSH (red). This, in turn, stimulates the production of thyroxine by the thyroid (blue). Thyroxine levels decrease TRH and TSH production by a negative feedback process.
TSH is secreted throughout life but particularly reaches high levels during the periods of rapid growth and development, as well as in response to stress. The hypothalamus, in the base of the brain, produces thyrotropin-releasing hormone (TRH). TRH stimulates the anterior pituitary gland to produce TSH.
Thyroid hormones (T 4 and T 3) are produced by the follicular cells of the thyroid gland and are regulated by TSH made by the thyrotropes of the anterior pituitary gland. The effects of T 4 in vivo are mediated via T 3 (T 4 is converted to T 3 in target tissues). T 3 is three to five times more active than T 4.
For example, thyrotropin-releasing hormone (TRH) is released from the hypothalamus in response to low levels of secretion of thyroid-stimulating hormone (TSH) from the pituitary gland. The TSH in turn is under feedback control by the thyroid hormones T4 and T3. When the level of TSH is too high, they feed back on the brain to shut down the ...
The neurohypophysis stores and releases two hypothalamic hormones: Oxytocin stimulates powerful uterine contractions, which trigger labour and delivery of an infant, and milk ejection in nursing women. Its release is mediated reflexively by the hypothalamus and represents a positive feedback mechanism.
The hypothalamus controls the anterior pituitary's hormone secretion by sending releasing factors, called tropic hormones, down the hypothalamo-hypophysial portal system. [3] For example, thyrotropin-releasing hormone released by the hypothalamus in to the portal system stimulates the secretion of thyroid-stimulating hormone by the anterior ...
The hypothalamus secretes thyrotropin-releasing hormone (TRH) into portal veins, which carry this hormone to the anterior pituitary. Thyrotropin-releasing hormone is a relatively small peptide, containing only three amino acids.