Prolactin

About: Prolactin is a research topic. Over the lifetime, 22356 publications have been published within this topic receiving 609537 citations. The topic is also known as: lactotropin, & PRL,.

Differential effects of opiate peptides and alkaloids on anterior pituitary hormone secretion

Abstract: In order to investigate the opiate receptors involved in the control of anterior pituitary hormone secretion, five different opioid drugs were administered intravenously to groups of 6 normal male subjects. Morphine (10 mg), methadone (10 mg), pentazocine (30 mg), nalorphine (10 mg) and 0.25 mg of the met-enkephalin analogue, DAMME, all caused similar increases in circulating prolactin with falls in serum LH and cortisol. Methadone and DAMME also elevated GH and TSH; morphine elevated TSH but not GH, nalorphine GH but not TSH. After pentazocine neither GH nor TSH changed. FSH failed to change significantly after any drug. All these changes, except serum cortisol, were antagonised by 4 mg naloxone. Taking into account the known receptor subtypes preferentially activated by each opiate, it is suggested that prolactin secretion is modulated by epsilon-receptors and TSH by mu-receptors. The control of ACTH probably involves delta-or kappa-receptors, that for LH kappa-or epsilon-receptors. It is not possible on present data to allocate a specific receptor mediating the opioid control of GH.

Evidence for direct inhibition of ovarian function by prolactin

Abstract: There is no doubt that in breast-feeding women, suckling with its associated hyperprolactinaemia prevents the resumption of ovarian activity for prolonged periods (see McNeilly, 1979) The extent of this suppression varies greatly among species but in all for which there are adequate data it appears to depend critically upon the intensity of the suckling stimulus (Lamming, 1978) Our recent data from women show that in the pattern of suckling, frequency and duration, throughout the day, are both key factors in maintaining the elevation of basal levels of prolactin associated with lactation (McNeilly, Howie & Houston, 1980a; Howie & McNeilly, 1982) Suckling also releases large quantities of prolactin, maintaining a physiological hyperprolactinaemic state which is directly associated with the duration of lactational amenorrhoea (Delvoye, Badawi, Demaegd & Robyn, 1978; Duchen & McNeilly, 1980) The question remains, how does suckling suppress ovarian activity? The levels of prolactin in blood during peak lactation appear to be many times the requirement for production of milk It therefore becomes pertinent to ask whether this prolactin is released solely to stimulate milk production or whether it is involved directly in the suppression of ovarian activity If there is a direct involvement then there are two loci for this action; an effect at the hypothalamic-pituitary level or a direct effect on the ovary While the former has received some attention (see McNeilly, 1979, 1980a), relatively little information is available (for species other than the rat) on whether or how prolactin might act on the ovary and, in particular, how high levels might interfere or block follicular development during lactation (McNeilly, 1980b) The purpose of this paper is to review the evidence for a direct action of prolactin on the ovary in the context of the effects of prolactin in the control of normal ovarian cyclicity

Serial Serum Levels of Gonadotropins, Prolactin and Sex Steroids in the Nonpregnant and Pregnant Chimpanzee1

Abstract: Serum levels of FSH, LH, chorionic gonadotropin (CG), prolactin, estrone (EJ, estradiol-17β(E2), estriol (E3) and progesterone were measured at 2-3-day intervals in 4 chimpanzees through 2-3 menstrual cycles, and serially through subsequent pregnancies. The hormone patterns of the menstrual cycles were similar to those in man, with high levels of FSH in the early follicular phase, followed by rising E2 concentrations to a peak (up to 35 ng⁄dl) at or just before a midcycle LH⁄FSH peak. In most cycles therewas a secondary E2 rise and progesterone rose to values above 500 ng⁄dl during the luteal phase. There was no consistent pattern in prolactin levels through 3 menstrual cycles. A simultaneous increase in E2 and LH⁄CG levels and a fall in FSH about 10 days postovulation indicated fertilization and implantation. Other early signs of pregnancy were persistent luteal range progesterone concentrations and rising levels of E, and E3. Peak CG levels (56-154 IU⁄ml) occurred 30-50 days after the midcycle LH⁄FSH pe...

A Chronobiologic Abnormality in Luteinizing Hormone Secretion in Teenage Girls with the Polycystic-Ovary Syndrome

Abstract: We investigated possible abnormalities of central-nervous-system regulation of luteinizing hormone secretion in the polycystic-ovary syndrome by determining the plasma concentrations of luteinizing hormone over a 24-hour period in five teenage girls with the syndrome; profiles of prolactin and cortisol were also obtained. Four of the five patients had strikingly abnormal plasma luteinizing hormone profiles: whereas normal pubertal girls have a daily surge in secretion of luteinizing hormone that is coterminous with their nocturnal sleep period, our patients had surges that were grossly desynchronized from their sleep period, occurring seven to eight hours later in the daytime than normal. The chronobiologic disturbance involved only luteinizing hormone; the profiles of cortisol and prolactin were normal. This finding points to the central nervous system as the probable locus of the initiating pathophysiology of polycystic-ovary syndrome.