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,.

Dopamine receptor agonists for treating prolactinomas

Abstract: Prolactinomas are the most common hormone-secreting pituitary tumours and cause infertility and gonadal and sexual dysfunction in both sexes. The approach to prolactinomas has changed in the last 25 years thanks to the availability of dopaminergic drugs characterised by a potent prolactin-inhibitory effect, a tumour shrinking effect associated with a satisfactory tolerability. In more recent years, cabergoline 1-[(6-allelylergolin-8beta-yl)carbonyl]-1-[3-(dimethylamino) propyl]-3-ethyl-urea an ergoline derivative with potent, selective and long-lasting inhibitory activity on prolactin release, has been used to suppress prolactin secretion in women with hyperprolactinaemia. Cabergoline was shown to be significantly more effective than bromocriptine in inducing a complete biochemical response and clinical efficacy and was better tolerated than bromocriptine in the majority of patients. Notable tumour shrinkage until tumour disappearance was observed during cabergoline treatment in most patients with macroprolactinoma and it was also proven effective in patients resistant to or with a poor response to bromocriptine. In view of the limited data on cabergoline-associated pregnancies and the long half-life of the drug, it is currently recommended that women hoping to become pregnant, once ovulatory cycles have been established, should discontinue cabergoline therapy 1 month before they intend to conceive. However, no data concerning negative effects on pregnancy or offspring have been reported. The great efficacy of this compound together with its excellent tolerability makes this drug the current treatment of choice for the majority of patients with hyperprolactinaemic disorders.

Evidence that hypothalamic periventricular dopamine neurons innervate the intermediate lobe of the rat pituitary.

Abstract: The purpose of the present study was to provide neurochemical and endocrinological evidence that dopamine (DA) neurons terminating in the intermediate lobe of the rat pituitary originate in the periventricular nucleus of the hypothalamus. One week following surgical separation of the periventricular nucleus from the mediobasal hypothalamus, DA and 3,4-dihydroxyphenyl-acetic acid (DOPAC) concentrations in the intermediate lobe were reduced by 50%, and this was accompanied by an increase in plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentrations. In contrast, this procedure had no effect on concentrations of prolactin in the plasma, or DA or DOPAC in the median eminence, the region of the mediobasal hypothalamus containing terminals of tuberoinfundibular DA neurons. Electrical stimulation of the periventricular nucleus increased the ratio of DOPAC/DA in the intermediate lobe and reduced the concentrations of alpha-MSH in the plasma, whereas in these same animals the DOPAC/DA ratio in the median eminence and concentrations of prolactin in the plasma were unaltered. These results indicate that approximately 50% of all the DA neurons terminating in the intermediate lobe of the rat pituitary originate in or project through the periventricular nucleus of the hypothalamus, and that these DA neurons regulate the secretion of alpha-MSH from intermediate lobe melanotrophs.

In cow anterior pituitary, growth hormone and prolactin can be packed in separate granules of the same cell.

Abstract: The ultrastructural localization of growth hormone and prolactin in cow anterior pituitary was studied by double immunocytochemical labeling using specific antibodies and protein A-gold particles of different sizes. The two hormones were found in specific somatotrophs and mammotrophs as well as in somatomammotropic cells which were multinucleated and predominantly arranged in clusters in the central area of the lobules. In these mixed cells the two hormones were packaged (a) in different granules of the same cell, (b) in the same granules where they were segregated in different portions of the granule content, or (c) in the same granules but evenly intermixed. The relative proportion of these three types of granules varied in somatomammotrophs of different animals. A single large Golgi complex was generally present in somatomammotrophs. Small, immature granules containing either growth hormone or prolactin or both hormones were found randomly distributed along Golgi stacks. This suggests that in these cells the two hormones are processed in the same Golgi cisternae and that mechanism(s) exist(s) to sort out the two hormones from each other.

Release of growth hormone in lactating and non-lactating goats in relation to behaviour, stages of sleep, electroencephalograms, environmental stimuli and levels of prolactin, insulin, glucose and free fatty acids in the circulation

Abstract: Recording electrodes were implanted in contact with the dura mater overlying the parietal cortex of six female goats, four of which were lactating. After recovery from surgery and complete familiarization with the housing conditions, the personnel and the recording technique, each goat was observed continuously for 24 h with simultaneous recording of the cortical electroencephalogram (EEG). Remote blood sampling was carried out every 30 min without disturbing the animal. Apart from the release of growth hormone (GH) associated with morning milking in two of the goats, there was no consistent relationship between the apparently spontaneous, episodic release of GH and behvaiour, stages of sleep, cortical EEG, air temperature, time of day or night, obvious environmental stimuli which arose from the normal husbandry routine, or the levels of porlactin, insulin, glucose or free fatty acids in the blood. There was also no relationship between the release of prolactin and the stages of sleep.