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G Lizarralde

Publications and source records attributed to G Lizarralde.

35 records · Page 2Linked to original sources
PubMed1987

Effect of ketoconazole on the 11-hydroxylation step of adrenal steroidogenesis.

We studied the effect of ketoconazole on glucocorticoid metabolism in three patients before and after a continuous four-hour infusion of ACTH. A single 400 mg oral dose of ketoconazole caused a decrease in serum cortisol concentration, while the concentration of 11-deoxycortisol and its ratio to cortisol increased. The decrease in serum cortisol levels was not accompanied by an increase in plasma ACTH concentration. A four-hour continuous infusion of ACTH resulted in an appropriate elevation of serum cortisol, but with a marked increase in serum concentration of 11-deoxycortisol and its ratio to serum cortisol. We conclude that 400 mg of ketoconazole can decrease cortisol synthesis apparently through a partial block of the 11-beta-hydroxylation step; the observed degree of inhibition may not be sufficient to stimulate the hypothalamic-pituitary-adrenal axis or to cause overt symptoms or signs of adrenal insufficiency; and this partial block of the 11-beta-hydroxylation step becomes more evident during a continuous infusion of ACTH, which can stimulate a normal response of cortisol.

Administration, Oral↗
PubMed1978

Amenorrhea and edema.

In a 22 year old woman extensive edema developed during evaluation for amenorrhea. It was learned then that she was consuming escessive amounts of a laxative daily. Balance studies were performed which demonstrated that she excreted large amounts of sodium in her liquid stools while taking the dose of laxative she had been using. The presence of increased plasma renin activity and increased urinary aldosterone suggest that in this patient the occurrence of the edema after she discontinued use of the laxative was due to secondary aldosteronism presumably caused by plasma volume depletion.

Adult↗
PubMed1978

Myxedema coma and normal serum thyroxine.

A 76-year-old man who developed the clinical syndrome of myxedema coma was found to have a normal serum thyroxine concentration. Further investigation revealed the presence of a low serum T3 level before and after sodium levothyroxine therapy when the serum T4 value was in the hyperthyroid range. In addition, he demonstrated an inability to release TSH after intravenous administration of TRH and was found to have an enlarged sella turcica. A partial defect in peripheral conversion of T4 to T3 is postulated.

Aged↗
PubMed1977

Nelson's syndrome: case report and review of the literature.

A patient who developed a pituitary tumor after adrenalectomy for Cushing's disease (Nelson's syndrome) is presented. The literature reviewed shows less than a 10 percent incidence of this disorder for which extremely elevated plasma ACTH levels are diagnostic. Special radiologic technics may be required to detect small pituitary tumors, but pituitary hormone levels may be elevated in the cerebrospinal fluid if there is suprasellar tumor extension. The different modalities available for treatment of Nelson's syndrome are discussed.

Adrenocorticotropic Hormone↗
PubMed1974

Myxedema crisis.

Explore the source record for details and available documents.

Electrocardiography↗
PubMedDate not supplied

Spectrum of the pulsatile characteristics of LH release in normal men.

To assess the spectrum of LH pulse characteristics in normal men, blood samples from 36 individuals were drawn at 20-minute intervals for 8 hours. The subsequent immunoactive LH concentrations were analyzed by computer algorithms to delineate the frequency and amplitude characteristics of pulsatile LH secretion. The absolute range for LH pulse frequency estimated by a modified threshold method was 1-6 pulses/8 hr, with a mean (+/- SEM) of 3.36 +/- 0.17 (median -3)pulses/8 hr. The distribution differed significantly from a Gaussian pattern. The mean LH pulse amplitude expressed as a percent increase above nadir was 92.1 +/- 6.1 (median-91.5%). When LH pulse amplitude was defined as an increment (mIU/ml) above nadir, the mean value was 5.13 +/- 0.4 (median -4.8) mIU/ml. These two expressions of amplitude were positively correlated (P less than 0.01), while the incremental (mIU/ml) pulse amplitude correlated inversely with pulse frequency (P less than 0.01). To examine the influence of more intensified rates of venous sampling on the spectrum of LH pulse properties, blood was sampled at 4-minute intervals for 8 hours in a subgroup of 13 men. Under these conditions, estimated LH pulse frequency was significantly higher, with a mean of 10.31 +/- 1.87 (median -9) pulses/8 hr compared with 20-minute sampling in the same individuals (P less than 0.001). Although the estimates of LH pulse frequency at 4-minute and 20-minute sampling intervals were significantly correlated (P less than 0.01), the dispersion of the LH pulse frequency estimates was considerably larger at more rapid rates of sampling. There was an absolute range of 2-20 pulses/8 hr for the 4-minute sampling, and 1-6 pulses/8 hr for the 20-minute sampling in the same individuals. This increase in LH pulse frequency and the broader dispersion of the range of frequencies estimated at 4-minute compared with 20-minute sampling intervals were confirmed using either another pulse detection algorithm, or separate criteria designed to adjust false-positive error rates in relation to sampling intensity. It was concluded that eugonadal men exhibit a broad spectrum of pulsatile LH characteristics, and the range of LH pulse attributes is even greater at more intensive rates of venous sampling. The results of this study in normal men demonstrate that a wider dispersion of physiologic LH pulse characteristics must be recognized in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMedDate not supplied

Alterations in the pulsatile properties of gonadotropin secretion in alcoholic men.

The functional characteristics of the hypothalamic-pituitary-testicular axis were examined quantitatively in 10 chronic alcoholic men without hepatic dysfunction or clinical nutritional deficiencies. Spontaneous gonadotropin pulsatility was analyzed in blood sampled every 20 minutes over a 24-hour period 3 to 16 days after abstinence from alcohol and again 29 to 39 days later. The numbers of LH and FSH pulses per 24 hours were normal in these alcoholic men compared with controls. However, we found increased mean 24-hour concentrations of immunoactive LH (P = 0.012) and FSH (P = 0.018), increased peak heights for LH (P = 0.035) and FSH (P = 0.004), decreased fractional LH (P = 0.002) and FSH (P = 0.044) pulse amplitudes and increased interpulse valley mean LH (P = 0.010) and FSH (P = 0.018) concentrations. Serum levels of total testosterone, total estradiol and estrone were normal, whereas concentrations of free testosterone and free estradiol were increased. Pituitary release of LH and FSH was normal in response to low (5-micrograms) and high (95-micrograms) doses of GnRH given intravenously. The present observations indicate that in chronically alcoholic men, acute abstinence from ethanol is associated with elevated circulating concentrations of immunoactive gonadotropins in the presence of intact spontaneous gonadotropin pulsatility, preserved pituitary responsiveness to exogenous GnRH, and increased concentrations of free testosterone and free estradiol. Such findings are consistent with alterations in the endogenous feedback actions of sex steroid hormones in this setting.

Adult↗
PubMedDate not supplied

24-hour pulsatile and circadian patterns of cortisol secretion in alcoholic men.

Pulsatile and circadian patterns of cortisol secretion during acute (3 to 16 days) and chronic (29 to 39 days) abstinence were examined in alcoholic men with no clinical or laboratory evidence of hepatic dysfunction or nutritional deficiencies. Mean and integrated 24-hour serum concentrations of cortisol determined by sampling the blood every 20 minutes over a 24-hour period were increased in six out of 10 alcoholic subjects during acute abstinence when compared with normal controls. Sustained abstinence in seven subjects with follow-up studies caused significant decreases in the mean maximal cortisol peak amplitude (13 +/- 1.0 SEM acutely vs. 10.3 +/- 0.52 micrograms/dl follow-up; P = 0.01), mean 24-hour serum cortisol concentrations (10.9 micrograms/dl +/- 1.2 vs. 8.5 micrograms/dl +/- 0.26; P = 0.047), interpulse valley mean (9.3 micrograms/dl +/- 0.88 vs. 6.5 micrograms/dl +/- 0.34; P = 0.007), and valley nadir (7.9 micrograms/dl +/- 0.69 vs. 5.4 micrograms/dl +/- 0.30; P = 0.0036) concentrations. Cortisol pulse frequency was normal. Although circadian cortisol rhythmicity was maintained in alcoholics, the timing of the circadian acrophase was delayed significantly (P = 0.006) during acute abstinence (1022 [clocktime] +/- 34 min) as compared with normal controls (0743 [clocktime] +/- 34 min), and the amplitude of circadian cortisol rhythms exceeded normal in five of 10 alcoholics. Analysis of data in one alcoholic subject by a new multiparameter deconvolution method demonstrated increases in secretory burst amplitude (0.64 microgram/dl +/- 0.08 SD), mass of cortisol released per burst (9.8 micrograms/dl +/- 1.2 SD), and daily endogenous cortisol production rate (22 mg +/- 2.4 SD) during acute abstinence. These values were statistically different when compared with seven normal controls and the subjects' values during sustained abstinence (P less than 0.02). In conclusion, the results of the present study suggest increased daily production of cortisol as a possible mechanism underlying the elevated serum cortisol concentrations in chronic alcoholics during acute abstinence. This abnormality is shown to be reversible with sustained abstinence from alcohol.

Adult↗
PubMedDate not supplied

Combined deficits in the somatotropic and gonadotropic axes in healthy aging men: an appraisal of neuroendocrine mechanisms by deconvolution analysis.

We have employed deconvolution analysis of 24-h serum GH, LH, and FSH concentration profiles to evaluate the nature of age-associated changes in GH, LH, and FSH secretion and disappearance in healthy older individuals. Our findings indicate that healthy aging results in a diminished frequency of detectable GH secretory episodes and an apparent decrease in estimated GH half life in men. These combined effects lead to a significant reduction in mean serum GH concentrations over 24 h. In contrast, we find that LH secretory burst frequency tends to increase with a reciprocal decrease in amplitude as serum total and free testosterone concentrations decline during healthy aging. There is also a prolongation of LH secretory burst duration, and a putative increase in basal LH secretion rates. The changes in LH secretory dynamics are specific, because the half life of immunoradiometric LH and the mass of hormone secreted per burst are not altered. In contrast, the apparent half life of FSH increases with age, and the secretory burst duration may decrease. This spectrum of distinct neuroendocrine sequelae of aging has interesting implications to both investigative and therapeutic strategies for modifying the somatotropic and gonadotropic axes in aging individuals.

Adult↗
PubMedDate not supplied

Patterns of cyclic 3'5'-adenosine monophosphate excretion in parathyroid dysfunction.

The pattern of excretion of cyclic 3'5' adenosine monophosphate (cAMP) over 24 h was evaluated in nine hyperparathyroid, four hypoparathyroid and three postoperative hyperparathyroid patients. The hyperparathyroid patients had increased excretion at the time of the normal nadir and were normal or low occasionally during the day. The pattern in the hypoparathyroid and in the postoperative patients also differed from normal. These findings suggest that both peaks of urinary cAMP excretion found in normal individuals result from the effects of parathyroid hormone on the kidneys.

Circadian Rhythm↗