Topic
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,.
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338 citations
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TL;DR: It is demonstrated that the normal process of aging involves alterations in the central mechanisms controlling the temporal organization of endocrine release in addition to a reduction of secretory outputs.
Abstract: To delineate the physiological effects of aging on basal levels and temporal patterns of neuroendocrine secretions, the 24-h profiles of cortisol, thyroid-stimulating hormone (TSH), melatonin, prolactin, and growth hormone (GH) levels were simultaneously obtained at frequent intervals in eight healthy, active elderly men, age 67-84 yr and in eight young male adults, age 20-27 yr. The study was preceded by an extended period of habituation to laboratory conditions, and sleep was polygraphically recorded. Mean cortisol levels in the elderly were normal, but the amplitude of the circadian rhythm was reduced. Circulating levels of daytime and nighttime levels of both TSH and GH were greatly diminished in old age. In contrast, prolactin and melatonin concentrations were decreased during the nighttime only. The circadian rises of cortisol, TSH, and melatonin occurred 1-1.5 h earlier in elderly subjects, and the distribution of rapid-eye-movement stages during sleep was similarly advanced, suggesting that circadian timekeeping is modified during normal senescence. Despite perturbations of sleep, sleep-related release of GH and prolactin occurred in all elderly men. Age-related decreases in hormonal levels were associated with a decrease in the amplitude, but not the frequency, of secretory pulses. These findings demonstrate that the normal process of aging involves alterations in the central mechanisms controlling the temporal organization of endocrine release in addition to a reduction of secretory outputs.
337 citations
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TL;DR: Retrograde transport ofpituitary hormones in the pituitary stalk vasculature was investigated in anesthetized male rats in which the pituitsary gland was intact and in animals in which it had been removed 30 to 60 min before use.
Abstract: Retrograde transport of pituitary hormones in the pituitary stalk vasculature was investigated in anesthetized male rats in which the pituitary gland was intact and in animals in which the anterior pituitary, posterior pituitary, or entire pituitary gland had been removed 30 to 60 min before use. Blood was collected for 1.5 to 2 h by free flow from a single long portal vessel through a microcannula, the tip of which was pointed toward the hypothalamus. An arterial blood sample was obtained at the end of each collection of portal blood. The concentrations (ng\ml) of LH, TSH, prolactin, ACTH, α-MSH, and vasopressin, determined by radioimmunoassay, in portal plasma from rats with intact pituitary glands were as follows: LH, 2,320 ± 874 (mean and SE); TSH, 10,180 ± 1,471; prolactin, 4,858 ± 884; ACTH, 82 ± 17.0; a-MSH, 103 ± 17.8; vasopressin, 2.4 ± 1.0. The concentrations of these hormones in arterial plasma of these rats were as follows: LH, <20; TSH, 149 ± 22; prolactin, 25 ± 5.0; ACTH, 0.36 ± 0.05; α-MSH,...
335 citations
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TL;DR: It is quite possible that the increased immune response in females allows them to compensate for the increased physiological stress which accompanies reproduction, and the final outcome would thus be the assurance of reproductive success of the species.
334 citations
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TL;DR: All typical antipsychotic medications are associated with sustained hyperprolactinaemia due to their high affinity for the D2 receptor and their slow dissociation from the receptor once bound, but atypicals differ quite dramatically in their propensity to cause prolonged high prolactin levels.
Abstract: Dopamine (DA) holds a predominant role in the regulation of prolactin (PRL) secretion. Through a direct effect on anterior pituitary lactotrophs, DA inhibits the basally high-secretory tone of the cell. It accomplishes this by binding to D2 receptors expressed on the cell membrane of the lactotroph, activation of which results in a reduction of PRL exocytosis and gene expression by a variety of intracellular signalling mechanisms. The hypothalamic dopaminergic neurons, which provide DA to the anterior pituitary gland, are themselves regulated by feedback from PRL through a 'short-loop feedback mechanism'. A variety of other modulators of prolactin secretion act at the hypothalamic level by either disinhibition of the dopaminergic tone (e.g. serotonin, GABA, oestrogens and opioids) or by reinforcing it (e.g. substance P). All typical antipsychotic medications are associated with sustained hyperprolactinaemia due to their high affinity for the D2 receptor and their slow dissociation from the receptor once bound, but atypicals differ quite dramatically in their propensity to cause prolonged high prolactin levels. Of those atypicals that are associated with prolactin elevation, the main causative factor appears to be a higher peripheral-to-central dopamine receptor potency of either the parent drug or its active metabolite (e.g. risperidone, 9-hydroxy-risperidone and amisulpride). Antipsychotics that easily cross the blood-brain barrier and exhibit fast dissociation from the dopamine receptor once bound do not result in sustained hyperprolactinaemia.
333 citations