The Journal of clinical endocrinology and metabolism
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J. Clin. Endocrinol. Metab. · Aug 1986
The circadian pattern of melatonin and its positive relationship with progesterone in women.
To investigate the possible role of melatonin in the regulation of the human menstrual cycle, the circadian pattern of melatonin was determined in the follicular and luteal phases of 10 normal women. Four-hourly sampling was used to derive a melatonin index which described the total exposure to melatonin for 24 h. This sampling procedure adequately represented the circadian melatonin output and demonstrated that pulses of melatonin secretion, inconsistent with a measured half-life of 47 min, did not exist. ⋯ To investigate the influence of exogenous progestins on the melatonin pattern, repeated 24-h profiles were measured in 8 women taking the 3-phase contraceptive pill. There was a significant increase (P less than 0.01) in the melatonin index associated with an increase in the dose of progestin. These results are consistent with a positive relationship between melatonin and progesterone and suggest that changes in the circadian pattern of melatonin secretion, rising during the luteal phase with a fall before ovulation, may act as a modulator of cyclicity.
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J. Clin. Endocrinol. Metab. · Jun 1986
Reversible hypopituitarism in patients with large nonfunctioning pituitary adenomas.
Detailed pituitary function studies were conducted on 26 patients with large nonfunctioning pituitary adenomas before and 2-3 months after transsphenoidal adenomectomy. Basal serum PRL, GH, TSH, LH, FSH, and ACTH levels were measured, and dynamic studies of their secretion were made. Preoperatively, GH deficiency was found in all 26 patients (100%), hypogonadism in 25 patients (96%), hypothyroidism in 21 patients (81%), and adrenal insufficiency in 16 patients (62%). ⋯ A rise in serum TSH levels in response to TRH stimulation preoperatively suggested the presence of viable pituitary tissue in these patients with hypopituitarism. The presence of a normal or mildly elevated serum PRL level before surgery also suggested the presence of functioning pituitary lactotrophs. These observations suggest that compression of the portal circulation is a possible mechanism for hypopituitarism in this setting.(ABSTRACT TRUNCATED AT 400 WORDS)
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J. Clin. Endocrinol. Metab. · May 1985
Effects of hypophysiotropic factors on growth hormone and prolactin secretion from somatotroph adenomas in culture.
In an attempt to characterize GH and PRL secretion in acromegaly, the effects of various stimuli on GH and PRL release by cultured pituitary adenoma cells derived from acromegalic patients were studied. In addition, the PRL responses of somatotroph adenoma cells were compared to those of prolactinoma cells. GH-releasing hormone-(1-44) (GHRH) consistently stimulated GH secretion in all 14 somatotroph adenomas studied in a dose-dependent manner. ⋯ TRH induced a significant increase in PRL secretion in only one prolactinoma. These results suggest that responsiveness to GHRH and somatostatin is preserved in somatotroph adenomas; the responsiveness to GHRH is inversely correlated to that to dopamine; and PRL cells associated with somatotroph adenomas possess characteristics similar to those of GH cells. Further, the GH stimulatory actions of TRH and VIP are different.
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J. Clin. Endocrinol. Metab. · Apr 1985
Specific growth hormone receptors on human peripheral mononuclear cells: reexpression, identification, and characterization.
Although specific GH receptors have been demonstrated in various tissues of a number of species, the presence of GH receptors on human peripheral mononuclear cells (PMC) is controversial. Binding of human GH (hGH) to its receptor as the hypothesized initial step of hormone action was consequently studied using mononuclear cells from peripheral venous blood of normal subjects. Specific binding of [125I]hGH was rapid, reversible, and time and temperature dependent. ⋯ Scatchard analysis of [125I]hGH binding to PMC revealed a receptor with a mean affinity constant of 1.5 +/- 0.2 (+/- SD) X 10(9)/M-1 (n = 72) and a maximal binding capacity of 7.1 +/- 2.0 X 10(-11) M/10(6) cells. The concentrations of calcium, sodium, and magnesium ions in the incubation medium strongly influenced GH binding, whereas pH or potassium concentration did not. As interassay variation of the binding assay was low (14% for total binding; 6% for specific hGH binding), this direct approach to study tissue receptors for hGH in a human in vitro test was reproducible and should encourage the investigation of receptor regulation as well as the study of binding in human disease.
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J. Clin. Endocrinol. Metab. · Mar 1985
Transient hypogonadotropic hypogonadism caused by critical illness.
The effects of acute severe illness on pituitary-gonadal function were determined in 35 men and 19 women, including 12 who were postmenopausal. Seventeen men and 5 women had traumatic brain injury which resulted in coma. Twelve postmenopausal and 2 premenopausal women had intracranial vascular accidents. ⋯ The low testosterone concentrations are not due to reduced sex hormone-binding capacity. Based upon our data in postmenopausal women, hypogonadotropism also occurs in the presence of nonfunctioning gonads. Although our studies do not completely establish the pathophysiology of this disorder, they suggest a suprapituitary origin.