1. The plasma level of some hormones control by feed back mechanisms. If the circulating hormone level is increases, the hormone can control it’s synthesis by negative feed back regulation.
2. Conversely decrease circulating hormone level will positively regulate its synthesis by positive feed back regulation
3. Eg.hypothalamic pituitary target gland system, thyroid hormone, adrenal, ovarian testicular hormones.
4. Positive feed back regulation can be seen in secretion of progesterone which are required for the acute burst of LH secretion that result in ovulation and follicular luteinization and further production of these steroid hormones.
5. Negative feed back regulation - The levels of circulating hormones are regulated by a feed-back mechanism. Increased levels of circulating oestrogen and progesterone have in inhibitory effect on the hypothalamic neurons, which through GnRH decrease the secretion of FSH and LH.
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