BIPN100 D - More Hormones and Regulation A. Prolactin - We...

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More Hormones and Regulation A. Prolactin - We know prolactin is released from the Anterior Pituitary and is regulated by Hypothalamus. How is it regulated? - Well, the hypothalamus releases PRH and it will secrete prolactin, but what will inhibit this mechanism so that no prolactin is released? - Answer is Dopamine. The main regulation of prolactin is dopamine, which is also secreted from the hypothalamus. Mentioned Conditions in Class: 1) Pregnancy and Nursing - During pregnancy, there is increase levels of progesterone and estrogen these increases inhibit the release of prolactin, so the mother does not produce milk. - However, during nursing, stimulation from nipple suckling will activate mechanoreceptors and there will be a release of oxytocin and decrease secretion of dopamine therefore, prolactin is released due to stimulation of Ant. Pit. Gland by PRH. - As long as the stimulation is occurring every 3 to 4 hours then the reflex is active for increase production of prolactin if not, then reflex is not active and it is difficult to get the reflex activation and milk production. - Remember though, still need oxytocin let down to stimulate smooth muscles of nipples to contract. 2) Lactation can also act as a contraceptive. - How? Because prolactin inhibits Gonadotropin Releasing Hormones, FSH and LH. Therefore, without these hormones there will be no egg growth or implantation. 3) Problems - Pituitary glands are sites of tumors and these tumors can produce hormones too. a. Tumor can compress optic nerve by adding pressure to the pituitary stock get loss of outer visual fields. b. Most common tumor is pituitary occurs in the prolactin producing cells. - Tumor cells produce a lot of prolactin and it will inhibit GnRHs, which will result in pregnancy. This occurs is a lot of young females who look forward to pregnancy, but cannot get so. - Can give drugs that are dopamine agonists, which will inhibit prolactin production or remove the tumor surgically.
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This note was uploaded on 09/18/2009 for the course BIPN 100 taught by Professor French during the Spring '07 term at UCSD.

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BIPN100 D - More Hormones and Regulation A. Prolactin - We...

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