Adrenocorticotrophic hormone (ACTH) is controlled through a negative feedback loop. CRH from the hypothalamus signals the pituitary gland to make adrenocorticotrophic hormone (ACTH). ACTH then signals the adrenal glands to release glucocorticoids, such as cortisol. When glucocorticoid levels reach a threshold, the hypothalamus and pituitary make less CRH and ACTH.
Thyroid Stimulating Hormone (TSH) is controlled through a negative feedback loop. Thyrotrophin releasing hormone (TRH) from the hypothalamus signals the pituitary gland to make thyroid stimulating hormone (TSH), which signals the thyroid to make thyroid hormones. These hormones travel through the blood and are recognised by the hypothalamus and pituitary gland. When a threshold is reached, the hypothalamus makes less TRH and the pituitary gland makes less TSH. This reduces thyroid hormone levels.
Growth Hormone (GH) is controlled through a negative feedback loop. Growth hormone releasing hormone (GHRH) from the hypothalamus signals the pituitary gland to make growth hormone. Neurons (nerve cells) in the hypothalamus monitor growth hormone levels. When levels are high, the hypothalamus releases somatostatin, which stops the pituitary gland making growth hormone. These two hormones rise and fall in turn to keep growth hormone levels within a normal range.
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) are controlled through a negative feedback loop. The hypothalamus releases gonadotropin releasing hormone (GnRH), which signals the pituitary gland to make luteinising hormone (LH) and follicle stimulating hormone (FSH). In men, LH and FSH signal the testes to produce testosterone. In women, LH and FSH signal the ovaries to make estrogen and progesterone. When these hormones reach a threshold level, the hypothalamus makes less GnRH. The hypothalamus can also reduce GnRH production when prolactin levels are high. This in turn decreases pituitary production of FSH and LH.
Prolactin is mainly controlled by dopamine, a chemical produced by neurons (nerve cells) in the hypothalamus. Dopamine signals the pituitary to stop making prolactin. Rising and falling dopamine levels keep prolactin in a normal range.