Hormone prolactin

Structure—function relationships of prolactin among a variety of species have been pubUshed (17,18). Only one gene for prolactin appears to exist (19). Although classically placed in the category of simple protein hormones, prolactin can be glycosylated. Carbohydrate attachment occurs at Asn-31, where the consensus glycosylation sequence Asn—X—Ser is found. 

The prolactin receptor, PER, which regulates milk production in mammals, belongs to the same receptor class as the growth hormone receptor. In addition to binding the hormone prolactin, PER also binds and is activated by growth hormone. The extracellular domain of PER forms a very stable 1 1 complex with growth hormone in solution this complex has been crystallized and its structure determined (Figure 13.21). We shall compare this structure with the 1 2 complex of the same hormone with GHR. 

Cannabimimetics are also shown to affect reproductive and metabolic functions indirectly by hormonal modulation through the hypothalamic and pituitary regulatory centers. They are found to reduce serum levels of the luteinizing hormone, prolactin, growth hormone, and thyroid-stimulating hormone, and to increase corticotropin (Murphy, 1998). 

Yet different elaboration of the same molecule affords a compound (162) that acts as an inhibitor to the pituitary peptide hormone prolactin, the factor responsible for supporting lactation. As such the drug has found use in suppressing lactation and in the treatment of prolactin-dependent breast tumors. 

Lactoferrin is the major whey protein present in breast milk (Teraguchi et ah, 1996) with many microbicidal properties (Leon-Sicairos et ah, 2006). The concentration of lactoferrin in milk has been reported as 1 g/liter in mature milk and 7 g/liter in colostrum (Houghton et ah, 1985). The concentration of lactoferrin in breast milk is controlled by the reproductive hormones prolactin and estrogen (Ward et ah, 2005). Lactoferrin has been demonstrated to resist digestion in the infant gut as it has been recovered intact from the stool of breast-fed infants (Bemt and Walker, 1999). Lactoferrin acts mainly in an iron-free state (apo-lactoferrin) and its microbicidal activity is reported to increase in proportion to its concentration in milk (Leon-Sicairos et ah, 2006). 

Inhibition of secretion of Growth hormone Thyroid-stimulating hormone Prolactin Acm... 

Bromocriptine also inhibits the secretion of the hormone prolactin and can be used to treat some problems of male and female infertility and impotence as well as menstrual discomfort. 

Mammary development is under the regulation of a complex set of hormones. Studies involving endocrinectomy (removal of different endocrine organs) show that the principal hormones are oestrogen, progesterone, growth hormone, prolactin and corticosteroids (Figure 1.4). 

Hormones detected in milk include some from the peptide and steroid classes but none of the amino hormones. Prolactin, a protein of 199 amino acid residues, is normally present in a concentration of about 50 /tg/liter, and the hexapeptide gonadotropin-releasing hormone of the hypothalmus at about 1.5 g/liter. Steroid hormones from the adrenal cortex include the glucocorticoids cortisol and corticosterone, totaling 0.2-0.6 /tg/liter. Those from the ovary—progesterone, estrone, and estradiol—have concentrations of 10-30, 30, and 175 /ig/liter, respectively. Hormones in milk have been reviewed by Koldovsky (1980) and Pope and Swinburne (1980). The prolactin in milk is biologically active (Gala et al. 1980). 

The adenohypophysis is the part of the gland in which the tropic hormones are secreted They include the adrenocorticotropic hormone lACTHl. die thyrotropic hormone (TSH). and. somatotropin, as well as three hormones with pronounced effects upon the gonads the hormone prolactin, the follicle-stimulating hormone tFSHl and the luteinizing or interstitial cell stimulating hormone tLH or ISCH)... 

Ovalbumin Conalbumin Ovomucoid Lysozyme Vitellogenin apo-VLDL Glucose-6-P-dehydrogenase Oviduct Oviduct (liver) Oviduct Oviduct Liver Liver Uterus Thyroid Hormones Carbamyl phosphate synthase Growth hormone Prolactin ( ) a-Glycerophosphate dehydrogenase Malic enzyme Liver Pituitary Pituitary Liver (mitochondria) Liver... 

Combined cytostatic drug therapy for Hodgkin s disease in childhood often results in abnormal endocrine function, particularly increases in follicle-stimulating hormone, prolactin, and thyroid-stimulating hormone (318). 

Several studies have suggested that single or short-term administration of G-CSF did not produce significant changes in the serum concentrations of cortisol, growth hormone, prolactin, follicle-stimulating hormone, luteinizing hormone, or thyrotropin (SEDA-20, 337 ... 

Increased serum levels of the anterior pituitary hormone prolactin are associated with secreting tumors of the gland and also with the use of centrally acting dopamine antagonists, especially the... 

Both in vitro and in vivo tests have shown that some of the eicosanoids affect the secretion of anterior pituitary hormones. PGE compounds promote the release of growth hormone, prolactin, TSH, ACTH, FSH, and LH. However, endocrine changes reflecting significant release of these hormones have not been reported in patients receiving PGE compounds. LTC4 and LTD4 stimulate LHRH and LH secretion (see below). 

Prolactin is a 198-amino-acid peptide hormone produced in the anterior pituitary. Its structure resembles that of growth hormone. Prolactin is the principal hormone responsible for lactation. 

B8. Bazan, J. F., A novel family of growth factor receptors A common binding domain in the growth hormone, prolactin, erythropoietin and IL-6 receptors, and the p75 IL-2 receptor beta-chain. Biochem. Biophys. Res. Commun. 164, 788-795 (1989). 

Fedele, M DeMartino, I., Pivonello, R., et al. (2007) SOM230, a new somatostatin analogue, is highly effective in the therapy of growth hormone/prolactin-secreting pituitary adenomas. Clin. Cancer Res. 13,2738-2744. 

Endocrine and metabolic Blood tests Serum concentrations of pituitary horrmones (TSH, LH, FSH, ACTH, growth hormone, prolactin, vasopressin) serum concentrations of other hormones (insulin parathyroid hormone, glucagon, calcitonin, vitamin D) and serum electrolyte concentrations (sodium, potassium, calcium, magnesium)... 

Concentrations of (10-160) X 10-3IU/liter of TSH in blood can be measured. There is no cross-reactivity with hLH, hFSH, adrenocorticotropic hormone, prolactin, or hCG (Fig. 7). TSH in dried blood samples is stable at room temperature for at least 1 month. The mean coefficients of variation were 12.1% (within assay) and 14.0% (between assays). A good correlation... 

As a rule, a hypothalamic hormone should always control a hormone in the anterior pituitary. The pituitary hormones (e.g. follicle-stimulating hormone, prolactin, or thyrotropin) are then transported through the bloodstream to the secondary target organs, where, for example, they stimulate the production of corticosteroids in the adrenals or the formation of thyroxine in the thyroid. 

Prolactin (PRL) Protein, MW 20,000 Prolactin release factor (PRF) may or may not be identical to thyrotropin-releasing hormone Prolactin release-inhibiting factor (PIF) most likely dopamine Supports lactation... 

Andreassen B, Huth J, Tyson JE (1979) Plasma thyrotropinreleasing hormone, prolactin, thyrotropin, and thyroxine concentrations following the intravenous or oral adminis-... 

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