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Results for “PITUITARY HORMONES”

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At least 811 records · Page 45Linked to original sources
PubMed1977

The effect of stressful diagnostic studies and surgery on anterior pituitary hormone release in man.

The hormonal response of the anterior pituitary was studied in 10 normal males undergoing treadmill exercise testing, in 5 male patients undergoing diagnostic gastroscopy, and in 8 male patients undergoing elective surgery under general anaesthesia. Serum TSH was depressed below the baseline value at 2 and 3 h post-treadmill exercise, at 1, 2 and 3 h post-gastroscopy and from 10 min through 2 h post-surgery. Serum triiodothyronine was depressed below the baseline value at 10 min through 2 h post-surgery. Serum prolactin, growth hormone and cortisol were elevated by all three stressful procedures. Both gastroscopy and surgery resulted in an elevation of serum luteinizing hormone levels. There was no significant change in serum FSH levels in any of the three procedures. The post-stress depression in TSH levels could result from the suppressive effect at the hypothalamic-pituitary level of high serum levels of cortisol generated by the stress of the procedures.

Adult↗
PubMed1991

Analysis of the copulsatility of anterior pituitary hormones.

We have used combinatorial algebra and computer simulations to calculate expected means, variances, and probabilities of hormone-peak coincidences in 2 or more endocrine pulse series. We illustrate application of this conditional probability analysis to pulsatile LH, FSH, and/or PRL data. We observed that 1) serum LH and FSH pulses in 14 young men were randomly associated on different days (P greater than 0.10), but highly synchronized on any given day (P less than 0.0001); 2) serum LH and FSH (P less than 0.0001), LH and PRL (P = 0.023), and FSH and PRL (P = 0.0003) peaks were significantly coupled in healthy postmenopausal women; and 3) the number of triple coincidences among LH, FSH, and PRL release episodes in postmenopausal women significantly exceeded chance expectations (P less than 0.0001). We conclude that suitable statistical coincidence analysis can offer an informative tool with which to evaluate nonrandom event concordance in endocrine investigations, such as clinical studies of the temporally coordinated release of anterior pituitary hormones.

Adult↗
PubMed1979

Membrane potential changes caused by thyrotropin-releasing hormone in the clonal GH3 cell and their relationship to secretion of pituitary hormone.

Effects of thyrotropin-releasing hormone (TRH; thyroliberin) on membrane electrical properties were studied in the clonal rat anterior pituitary cell (GH3) by continuous recording of the intracellular potential. Application of TRH, which stimulates the release of prolactin and growth hormone from the GH3 cell, elicited a transient hyperpolarization of the cell membrane followed by an enhancement of the generation of action potentials for an extended period in the majority of cells tested. The transient hyperpolarization was due to an increase of the membrane conductance to K+. The enhancement of the spike generation was not due to membrane depolarization. The input resistance of the cell membrane was found to be increased during the facilitation. Thus the mechanism of the facilitatory action of TRH is different from the mechanisms of conventional excitatory neurotransmitters. TRH enhances the spike generation, thus promoting Ca2+ entry from extra- to intracellular space (the action potential of the GH3 cell has a Ca2+ component) and stimulating the release of hormones. This notion is supported by the observation that cobalt ions, which block the calcium spike in these cells, completely abolished the stimulatory effect of TRH on the release of prolactin and growth hormone.

Action Potentials↗
PubMed1989

Anterior and posterior pituitary hormone release induced in sheep by cholecystokinin.

The effect of an intravenous bolus injection of cholecystokinin octapeptide (CCK-8; 0.85 micrograms/kg) on the release of cortisol, prolactin, vasopressin, and oxytocin was studied in sheep (n = 10). Concentrations of these hormones were measured in blood samples taken before (-10, 0 min) and after (5, 10, 20 min) administration of a saline vehicle or vehicle + CCK. Following CCK treatment, levels of cortisol were raised after 10 and 20 min, prolactin and vasopressin concentrations were increased after 5 min, and oxytocin secretion was unaffected.

Animals↗
PubMedDate not supplied

Circadian rhythms of anterior pituitary hormone secretion: effects of dexamethasone.

Circadian rhythms of hormone secretion are by now well recognized but there are limited data available to compare such rhythms of multiple hormones in individual subjects. Therefore concentrations of serum thyrotropin (TSH), cortisol, growth hormone (GH), triiodothyronine (T3) and prolactin (PRL) were determined in blood samples from six healthy males over periods of 24 hours. A circadian periodicity was identified for cortisol, GH, PRL and TSH; maximum concentrations for TSH and PRL occurred at dissimilar times, namely respectively before and after the GH peak. Maximum TSH coincided with nadir values forplasma cortisol. Dexamethasone administration (3 mg over 36 hours) lowered serum T3 concentration and abolished TSH periodicity without affecting the PRL rhythm. These data suggest that a) nocturnal TSH and PRL maximum levels do not have common mediation; b) there may be an inverse relationship between cortisol and TSH, and c) glucocorticoids at low doses preferentially affect secretion of thyrotropin.

Adult↗
PubMed1995

Further studies on the role of cholecystokinin-A and B receptors in secretion of anterior pituitary hormones in male rats.

We compared the effects of unselective cholecystokinin (CCK) agonists (caerulein and CCK-8s) and a CCKB agonist CCK-4 on the secretion of thyrotropin (TSH), growth hormone (GH) and prolactin (PRL) in male rats. The subcutaneous (s.c.) administration of caerulein and CCK-8s suppressed dose-dependently TSH and GH levels. In contrast, when given into the 3rd brain ventricle (i.c.v.) caerulein dose-dependently elevated the GH levels. Next the importance of the afferent vagal nerves was studied in the action of caerulein and CCK-4. Subdiaphragmatic vagotomy itself decreased cold-stimulated TSH levels but abolished the suppressing effect of intraperitoneal (i.p.), and apparently also that of the i.c.v. caerulein. GH and PRL levels were altered neither by vagotomy nor caerulein. CCK-4 did not affect hormone levels. Atropine and butylscopolamine (i.p.) themselves did not alter TSH, PRL or GH secretion in intact rats. Neither did they reverse the effect of caerulein on TSH. In conclusion, CCKA receptors dominate in TSH and CCKB receptors in GH regulation. CCKA receptors in the gastrointestinal tract, related to the nervus vagus are mediating the inhibitory effect of caerulein upon TSH secretion but inhibition of GH secretion does not depend on the nervus vagus. CCKB receptors in the brain stem or near the 3rd brain ventricle are responsible for stimulation of GH secretion.

Animals↗
PubMed1979

The effect of lisuride hydrogen maleate, an ergot derivative on anterior pituitary hormone secretion in man.

The effects of single oral doses of 0.2 mg of lisuride hydrogen maleate, a semisynthetic ergot derivative, on serum levels of prolactin (PRL), growth hormone (GH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH), cortisol and blood glucose were studied in six normal males. Lisuride effectively inhibited basal PRL secretion as well as the PRL response to TRH given 3 h later. In addition, the drug raised basal GH levels and decreased basal and TRH stimulated TSH secretion. No significant differences between lisuride and control were observed in basal LH and FSH, LHRH stimulated gonadotrophins or in cortisol. Drowsiness was noted by all subjects, one became nauseated and another vomited, 60 and 90 min respectively after administration of lisuride. No changes were seen in pulse rate and blood pressure. The endocrine effects of lisuride were attenuated by the prior administration of the dopamine antagonist metoclopramide. These results suggest that lisuride acts as a long-acting dopamine agonist and that therefore this drug could be of therapeutic use in hyperprolactinaemic states and acromegaly.

Adult↗
PubMed1986

Monoamine biosynthesis in hypothalamic regions of dwarf mice: effect of replacement of deficient anterior pituitary hormones.

Female Ames dwarf and phenotypically normal female mice were killed 30 min after treatment with NSD-1015, an aromatic L-amino acid decarboxylase inhibitor. The accumulation of dihydroxyphenylalanine (DOPA) and 5-hydroxytryptophan were measured by high-performance liquid chromatography with electrochemical detection and provided estimates of the endogenous biosynthesis of dopamine (DA) in the median eminence (ME) and serotonin biosynthesis (5-HT) in all brain regions which were examined. Dopamine synthesis was markedly suppressed in the ME while 5-HT synthesis was enhanced in both the ME and mediobasal hypothalamus (MBH) of dwarfs as compared to phenotypically normal mice. Overall, catecholamine biosynthesis (DOPA accumulation) was suppressed in the MBH of the dwarf mice but was not different from that observed in normal mice in the preoptic area anterior hypothalamus (POA-AH). The biosynthesis of 5-HT was not different in the POA-AH of dwarf mice as compared to normal mice. In the second experiment dwarf mice received saline vehicle, ovine prolactin (PRL), growth hormone (GH) or thyroxin (T4) daily for 14 days. Normal mice received saline only. Replacement with PRL significantly enhanced DA synthesis in the ME and was the only hormone to suppress significantly the elevation of 5-HT synthesis normally observed in the ME and the MBH of the dwarfs. Both GH and T4 only partially reduced 5-HT synthesis in the ME and MBH so that this parameter was no longer statistically different from either saline-treated dwarfs or normal mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗