Prolactin-inhibiting hormone

BIO. Ben-Jonathan, N Dopamine A prolactin-inhibiting hormone. Endocr. Rev. 6,564-589 (1985). 

The release of prolactin from the adenohypophysis is normally inhibited by prolactin-inhibiting hormone (PIH, dopamine) from the hypothalamus. Prolactin secretion is also controlled by prolactin-releasing factor (PRF). The release of PRF from the hypothalamus is mediated by reflexes elicited by suckling and breast stimulation. 

Prolactin secretion is under the inhibitory control of hypothalamus through prolactin inhibiting hormone (PRIH) which is a dopamine and acts on pituitary lactotrope receptor. 

Prolactin Inhibiting Hormone na na TIDA Inhibits PRL release, also indirectly Gia-AC inhibition... 

Prolactin-inhibiting hormone (PIH), also known as dopamine, is not a peptide (Chapter 17). It functions as a neurotransmitter in the CNS and as a precursor of norepinephrine and epinephrine in the adrenal medulla. In the hypothalamus, it originates in the TIDA and is released at the median eminence. Dopamine is a potent inhibitor of PRL release by the lactotropes (and mammosomatotropes) of the anterior pituitary, and this effect is mediated by D2 receptors that are coupled to Gj inhibition of adenylate cyclase. The lactotropes are unique in that they do not require stimulation by the hypothalamus to secrete PRL in fact, blockage of the blood flow from the hypothalamus to the anterior pituitary results in elevated serum levels of PRL, due to withdrawal of dopamine. Thus, unlike somatostatin, the effectiveness of dopamine does not depend on the presence of a stimulating hormone (Chapter 34). 

Definition of abbreviations ACTH, adrenocorticotropin hormone DA, dopamine FSH, follicle-stimulating hormone GH, growth hormone GnRH, gonadotropin-releasing hormone LH, luteinizing hormone PIH, prolactin-inhibiting hormone. 

F. Prolactin-Inhibiting Hormone (PIH, Dopamine) Dopamine is the physiologic inhibitor of prolactin release. Because of its peripheral effects and the need for parenteral administration, dopamine is not useful in the control of hyperprolactinemia, but bromocriptine and other orally active ergot derivatives (eg, cabergoline. pergolide) are effective in reducing prolactin secretion from the normal gland as well as from pituitary tumors. 

A 56-residue peptide, which is formed from the 10-kDa precursor to GnRH, inhibits secretion of prolactin.75 Inhibition of FSH release is accomplished by feedback inhibition. Hormones known as inhibins are produced in the gonads and act to inhibit release of FSH from the pituitary.76... 

Receptor Class Mu (pi) Primary Therapeutic Effect(s) Spinal and supraspinal analgesia Other Effects Sedation respiratory depression constipation inhibits neurotransmitter release (acetylcholine, dopamine) increases hormonal release (prolactin growth hormone)... 

Prolactin has been shown to increase LH receptor numbers in dwarf mice, seasonally repressed hamsters and hypophysectomized rats (see Ref. 6 for other references). In the hypophysectomized rats the combined effects of prolactin, growth hormone and LH were necessary to maintain the LH receptors [46]. The induction of hyperprolactinemia leads to increased LH receptors. Decreases in serum prolactin levels caused by treatment with compounds that inhibit the release of prolactin (dopamine analogues) decrease LH receptors (see Ref. 6 for other references). 

Bromocriptine was the first D2-receptor agonist to be used in the treatment of hyperprolactinemia and has been the mainstay of therapy for over 20 years. It inhibits the release of prolactin by directly stimulating postsynaptic dopamine receptors in the hypothalamus. Hypothalamic release of dopamine (prolactin-inhibitory hormone) inhibits the release of prolactin. Decreases in serum prolactin concentrations occur within 2 hours of oral administration with maximal suppression occurring after 8 hours, and suppressive effects persisting for up to 24 hours. Medical therapy with bromocriptine normalizes prolactin serum concentrations, restores gonadotropin production, and shrinks tumor size in approximately 90% of patients with prolactinomas. ... 

Prolactin release-inhibiting hormone or factor, prolactostatin. 

Prolactostatin, prolactin release-inhibiting hormone, PRIH or PIH, prolactin release-inhibiting factor, PRIF, a hypothalamic substance of (until now) unknown structure that inhibits the release of prolactin. 

Statins, release inhibiting factors, release inhibiting hormones, neurohormones synthesized in the small-cell region of the hypothalamus and transported via the bloodstream to the anterior pituitary. Members of the statins include melanostatin, somatostatin, and prolactostatin. They inhibit the secretion of melanotropin, somatotropin, and prolactin, respectively. Together with the corresponding liberins, the statins regulate the levels of the three pituitary hormones. 

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