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Results for “PITUITARY HORMONES”

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At least 667 records · Page 37Linked to original sources
PubMed1983

Altered pituitary hormone secretion in patients with pseudocyesis.

Pituitary function studies were performed in two patients with pseudocyesis, one of whom was reinvestigated during a recurrent episode. There was an exaggerated prolactin response to thyrotropin-releasing hormone, an aberrant growth hormone increase, and an impaired growth hormone response to dopamine receptor agonists (apomorphine or bromocriptine). These findings point to a derangement in hypothalamic-pituitary function in pseudocyesis and may indicate an underlying impairment in dopaminergic function in this disorder.

Adult↗
PubMed1993

[Action mechanism of pituitary hormones--receptor and signal transduction--prolactin].

The purification and identification of human prolactin (hPRL) had been delayed, compared with other pituitary hormones, until the determination of total amino acid sequence of hPRL in 1977. A full-length cDNA for the hPRL receptor was identified from hepatoma and breast cancer cell lines in 1989. Subsequent identification of cDNAs for PRL receptor of several species revealed that molecular size of PRL receptors could be classified into three forms, i.e., long, short and intermediate, according to the length of intracellular domain. The mechanism of post-receptor signal transduction has not been clarified yet. However, protein kinase C may be involved in this process. Further studies are necessary to investigate the relationship between molecular size of PRL receptor and postreceptor events.

Animals↗
PubMed1995

Effects of anandamide (endogen cannabinoid) on anterior pituitary hormone secretion in adult ovariectomized rats.

It has been shown that the main psychoactive component of marihuana, delta 9-tetrahydrocannabinol (THC) has mainly inhibitory effects on pituitary luteinizing hormone (LH), prolactin (PRL) and growth hormone (GH) and has no or little effect on follicle stimulating hormone (FSH) secretion. Recently the purification and availability of the putative endogenous ligand for the cannabinoid receptor, anandamide (arachidonyl ethanol-amide, anandamide) (ANA) provided us the opportunity to compare the effects of THC and ANA on the female neuroendocrine system in ovariectomized (OVX) rats. OVX was performed three weeks prior to the experimental period to avoid cyclic differences. OVX rats were injected i.p. with either THC or ANA (0.02 mg/kg.b.w./day, respectively) or vehicle for two weeks. The results show that both ANA and THC decrease serum LH level although THC with a higher degree. No significant differences were observed in serum FSH level. Both drugs decreased serum PRL. Serum GH was increased after THC administration and significantly decreased after ANA. The results indicate that ANA and THC alter pituitary hormone secretion, mainly by inhibitory action. The site of action requires further investigations.

Animals↗
PubMed2000

Cooperation of pituitary hormone prolactin with interleukin-2 and interleukin-12 on production of interferon-gamma by natural killer and T cells.

The pituitary hormone prolactin (PRL) is also produced by cells of the immune system and participates in early and late T cell activating events. We have previously shown a modulatory role of PRL during maturation of dendritic cells (DC). Production of IL-12 by T cell receptor (TCR)-activated DC is necessary for T cells to acquire the Th1 cytokine (i.e., IFN-gamma secreting) profile, which is associated with activation of cellular response. In a separate work, PRL has been shown to increase IFN-gamma synthesis by natural killer (NK) cells. We have extended that study by exploring the ability of PRL to induce IFN-gamma production by T and NK cells in the presence of the specific stimuli IL-12 and IL-2. The individual effect of PRL, IL-12, and IL-2 was specific for NK cells, and IL-2 and IL-12 were much more efficient than PRL. Cooperation of IL-2 and PRL was observed on NK cells. IL-2-induced synthesis of IFN-gamma was increased by physiological concentrations of PRL but was unaffected or inhibited by high concentrations. By contrast, optimal enhancement of IL-12-induced IFN-gamma release was observed with T cells but not with NK cells. Unexpectedly, interaction between PRL and IL-12 occurred only at high concentrations of PRL. These data indicate a complex role of PRL in the cytokine network and point to a revaluation of the proposed immunosuppression by stress-related hyperprolactinemia.

Cells, Cultured↗
PubMed2006

In vivo and in vitro effects of chromium VI on anterior pituitary hormone release and cell viability.

Hexavalent chromium (Cr VI) is a highly toxic metal and an environmental pollutant. Different studies indicate that Cr VI exposure adversely affects reproductive functions. This metal has been shown to affect several tissues and organs but Cr VI effects on pituitary gland have not been reported. Anterior pituitary hormones are central for the body homeostasis and have a fundamental role in reproductive physiology. The aim of this study was to evaluate the effect of Cr VI at the pituitary level both in vivo and in vitro. We showed that Cr VI accumulates in the pituitary and hypothalamus, and decreases serum prolactin levels in vivo but observed no effects on LH levels. In anterior pituitary cells in culture, the effect of Cr VI on hormone secretion followed the same differential pattern. Besides, lactotrophs were more sensitive to the toxicity of the metal. As a result of oxidative stress generation, Cr VI induced apoptosis evidenced by nuclear fragmentation and caspase 3 activation. Our results indicate that the anterior pituitary gland can be a target of Cr VI toxicity in vivo and in vitro, thus producing a negative impact on the hypothalamic-pituitary-gonadal axis and affecting the normal endocrine function.

Acetylcysteine↗
PubMed1982

[Effects of bromocriptine and dopamine on pituitary hormone secretion in women].

The present study was designed to examine whether a dopamine agonist, bromocriptine (Brc) exerts similar effects as dopamine (DA) on the pituitary hormones secretion and also to investigate the interaction of these dopaminergic agents and a dopamine receptor antagonist, metoclopramide (MCP) on the DA receptors in the hypothalamic-pituitary axis. Thirty normal cycling women in the midfollicular phase volunteered for this study. Following the administration of Brc (2.5mg, orally) to 13 subjects, a partially significant fall in LH levels, but not in FSH levels, during 4h was observed. DA, infused at a rate of 5 micrograms/kg/min for 4h, induced a significant fall in LH levels between 1 and 4h, but in FSH levels only at 2.5h after the start of infusion in 9 subjects. The amplitude of the spontaneous pulsations of LH secretion which was observed in 8 control subjects, was diminished by DA, while the amplitude seemed to be augmented by Brc. The administration of MCP (10mg, i.v.) to all subjects at 3h during the 4h experimental period caused no observable change in LH and FSH levels. A significant and progressive decline in PRL levels was observed in both Brc-and DA-treated groups of subjects, and this PRL-lowering effect was markedly counteracted by MCP administration in DA-treated group, but not in Brc-treated group. Brc induced a widely varying but significant rise in GH levels, with which MCP did not appear to interfere, whereas DA failed to cause any significant changes in GH levels. These data suggest that Brc, in contrast with DA, seems to be able to increase the pulse amplitude, but not the basal level, of LH and to stimulate GH secretion. Brc is also regarded to be a potent and unique PRL inhibitor, because its PRL-lowering effect cannot be easily antagonized by MCP.

Adult↗
PubMed1984

Central catecholamine neurons and exposure to dichloromethane. Selective changes in amine levels and turnover in tel- and diencephalic DA and NA nerve terminal systems and in the secretion of anterior pituitary hormones in the male rat.

Subacute exposure of male rats to various concentrations (70-1000 ppm) of dichloromethane (DCM) produces a selective reduction of dopamine (DA) levels without a change of DA turnover in certain types of forebrain DA nerve terminal systems. In the low concentration (70 ppm) a selective reduction of DA turnover was observed in the medial palisade zone (MPZ) of the median eminence. This chlorinated organic solvent also produced a discrete dose-dependent increase of noradrenaline (NA) turnover within the anterior periventricular hypothalamic area and with the highest concentration an increase of NA turnover in the anteromedial frontal cortex. DCM reduced NA levels dose-dependently in the posterior periventricular hypothalamic area and also reduced NA levels in the dorsomedial hypothalamic nucleus (1000 ppm). Following tyrosine hydroxylase inhibition DCM produced an inversely dose-related increase of serum LH levels and at the highest concentration an increase of ACTH secretion was observed. It is suggested that DCM can produce discrete changes in amine storage and turnover in catecholamine (CA) nerve terminal systems of the tel- and diencephalon, some of which may contribute to the DCM induced disturbances of the secretion of anterior pituitary hormones but actions on other transmitter-identified neurons involved in neuroendocrine regulation must also be considered.

Animals↗
PubMed1993

Alteration of serum pituitary hormone levels in postmenopausal women with stroke.

BACKGROUND AND PURPOSE: The aim of this study was to determine if circulating levels of pituitary hormones are altered by stroke and, if so, whether these alterations offer insight into specific neurochemical pathways in the region of the central nervous system injury. METHODS: Twenty-eight consecutive postmenopausal women undergoing computed tomographic imaging of the brain for evaluation of clinical evidence of stroke underwent blood sampling for determination of serum levels of luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone, triiodothyronine, prolactin, estradiol, and sex hormone--binding globulin. RESULTS: In stroke involving the caudate, serum levels of luteinizing hormone and follicle-stimulating hormone were reduced to 16% and 24% of concentrations found in those with stroke outside of the basal ganglia (p < 0.03 and p < 0.01, respectively). Levels of estradiol, sex hormone-binding globulin, thyroid-stimulating hormone, and prolactin were similar in all stroke groups. Nonspecific biochemical effects of stress that might influence hormone concentrations were assessed by measurement of serum triiodothyronine, the level of which is a sensitive biochemical correlate of disease severity. These levels were not different between stroke groups. CONCLUSIONS: Stroke involving the caudate nucleus may interrupt neurotransmitter pathways involved in control of secretion of gonadotropins. Peripheral levels of these hormones may serve as a marker for central neurochemical disturbances associated with stroke in specific brain regions.

Aged↗
PubMed1983

Differential effects of a dopaminergic drug (piribedil) on pituitary hormone release in normal men and women.

Six normal women, in the follicular phase of their menstrual cycle, and 6 normal men received orally 40, 60 and 100 mg doses of piribedil, a dopamine receptor agonist, or placebo. The effects of piribedil on anterior pituitary hormone release was evaluated. In normal women a dose-related decrease in Prl levels was observed, while in men the Prl decrement was not related to the dose employed. In women an increase in serum hGH occurred after administration of the lowest (40 mg) dose of piribedil. In normal men, on the contrary, a modest hGH stimulation was present after administration of all doses of the drug. No consistent changes in serum TSH, LH and FSH concentrations were observed and no side effects were reported. The results from this study indicate that piribedil can exert differential effects on hypophyseal trophic hormone release and that these effects are sex-related. It is possible that the differences observed in men and women after the administration of piribedil are due to a different endogenous dopaminergic tone, induced by the different sexual steroid environment.

Adolescent↗