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Biomedical subjects

A R Glass

Publications and source records attributed to A R Glass.

66 records · Page 4Linked to original sources
PubMed1979

The hypothalamic-pituitary-testicular axis in thyrotoxicosis.

The hypothalamic-pituitary-testicular axis was evaluated in seven men with thyrotoxicosis due to Graves' disease. Loss of libido and decreased potency were present in 71% and 56%, respectively. All patients had normal testicular volume (25 ml in all) and gynecomastia was detected in two of seven patients. Total sperm counts were less than 40 million in four of the five men tested. There was an inverse correlation between basal serum 17 beta-estradiol (E2) levels and total sperm count (r = -0.87; P less than 0.05). Mean (+/- SE) total testosterone (T) and E2 levels (1008 +/- 104 ng/100 ml and 104 +/- 16 pg/ml) were significantly higher than in normal men (P less than 0.05). Free T (13.6 +/- 2.4 ng/100 ml) was indistinguishable from normal (15.3 +/- 1.5 ng/100 ml). The mean (+/- SE) response of serum T to hCG administration was blunted (80 +/- 40%) compared to controls (193 +/- 19%; P less than 0.02). Basal plasma LH levels (15.5 +/- 1.5 mIU/ml) were significantly higher (P less than 0.05) than in normal men (9.1 +/- 0.6 mIU/ml) and hyperresponded to 100 microgram LRH iv in five of seven patients. Basal plasma FSH levels and the FSH response to LRH were normal. These results suggest that men with hyperthyroidism have 1) partial Leydig cell failure, 2) impairment of spermatogenesis, and 3) blunting of the feedback effects of E2.

Adult↗
PubMed1979

Gynecomastia after chemotherapy for lymphoma.

Although development of gynecomastia in a patient with cancer may indicate persistence or regrowth of a tumor, we studied three patients with lymphoma in whom development of gynecomastia during or after chemotherapy did not portend a poor outcome. In all patients, serum testosterone levels were normal, serum luteinizing hormone (LH) levels were high-normal or elevated, and serum follicle-stimulating hormone (FSH) levels were clearly elevated. The serum estradiol level of one patient was elevated at the onset of gynecomastia, but it fell to normal as the gynecomastia resolved spontaneously over a three-month period during which the patient received no chemotherapy. In a second patient, gynecomastia resolved over a period of eight months while the patient continued on maintenance chemotherapy, and he remains clinically well in remission 21/2 years after onset of gynecomastia. In the third patient, gynecomastia developed while the patient was in complete remission and off of all therapy, and it remained unchanged for the duration of a 21/2-year remission without therapy. Gynecomastia after chemotherapy for lymphoma is not an ominous prognostic sign and does not necessarily indicate the need for alteration of the treatment regimen.

Adult↗
PubMed1978

Secondary amenorrhea in obesity: etiologic role of weight-related androgen excess.

A massively obese, amenorrheic young woman had elevated levels of plasma androgens which could be reduced either acutely by dexamethasone administration or chronically by weight loss. Normalization of plasma androgen levels in both instances led to resumption of ovulation, suggesting that weight-related hyperandrogenism is a cause of amenorrhea in obesity.

Adult↗
PubMed1978

Serum triiodothyronine in undernourished rats: dependence on dietary composition rather than total calorie or protein intake.

Serum triiodothyronine (T3) in rats did not change if food intake was restricted without altering the composition of the diet. Feeding a hypocaloric low-protein high-carbohydrate diet caused increases in serum T3, while feeding a hypocaloric high-protein low-carbohydrate diet caused decreases in serum T3. These changes were not related to reductions in intake of either calories or protein, and concomitant changes in serum thyroxine (T4) were not observed. Reduction in the dietary content of valine, without changes in the percentage of carbohydrate in the diet, caused increases in serum T3 when compared to growth-matched controls on a diet with normal valine concentration. Serum T3 in undernourished rats depends on the composition of the diet and not on total intake of calories or protein.

Animals↗
PubMed1977

Serum gonadotropins in rats fed a low-valine diet.

Female rats fed a low-valine diet from the time of weaning have been shown to have delayed puberty compared to growth-matched controls. To explore the mechanism of this delay, serum LH and FSH were measured in rats fed the low-valine diet and in growth-matched control rats at several ages prior to puberty. Hormonal determinations at each time point were made both in the basal state and after LHRH administration or castration. After age 27 days, the mean basal serum FSH was lower in the low-valine group than in the control group. The mean serum levels of LH and FSH after oophorectomy were significantly lower in the low-valine group than in the control group, although the mean serum levels of LH and FSH after LHRH administration to intact animals were similar in both groups. The combination of impaired response to castration with unimpaired pituitary response to LHRH suggests that the low-valine group had a hypothalamic defect which accounts for their delayed sexual maturation when compared to growth-matched animals.

Aging↗
PubMed1976

Effect of undernutrition and amino acid deficiency on the timing of puberty in rats.

Sexual maturation was examined in underfed or amino acid-deficient rats. We have demonstrated a highly significant negative linear relationship (r = -0.80, P less than 0.001) between the age at puberty and the growth rate in rats under conditions of food restriction. The weight at puberty in animals growing at different rates because of undernutrition was not constant but behaved as a quadratic function of growth rate, as predicted from the assumption that growth rate was an independent variable. Growth rate is therefore more important than arrival at a particular fixed weight in determining the timing of puberty. Feeding of low valine diets resulted in delayed sexual maturation. Both the weight at vaginal opening (182 +/- 5.9 g) and the weight at first estrus (187 +/- 6.1 g) were significantly greater in the valine-deficient group when compared with growth-matched control (139 +/- 10.7 g and 161 +/- 9.3 g, respectively, P less than 0.05). The valine-deficient group also had significantly later vaginal opening (98.8+/- 4.7 days) than growth-matched controls (76.6 +/- 6.6 days, P less than 0.02). Valine deficiency seemed to have a specific effect on the hypothalamic-pituitary-gonadal axis since puberty in valine-deficient animals was delayed more than could be accounted for by impairment of growth.

Amino Acids↗
PubMedDate not supplied

Growth and reproductive adaptation in male rats with chronic protein deficiency.

In previous studies, male rats fed a low-protein diet beginning at weaning were found to have impaired sexual development through age 11 weeks when compared to food-restricted, weight-matched controls fed a diet with normal protein content. To determine whether male rats show long-term adaptation of the reproductive axis to low-protein feeding, we assessed sexual maturation and growth in rats fed a low protein (9%) diet from weaning until sacrifice at various points in time between ages 79 and 185 days. After age 80 days, there was no difference in reproductive organ weights (prostate, seminal vesicles, testis) or serum hormone levels (luteinizing hormone, follicle stimulating hormone, testosterone) between protein-deficient animals and food-restricted weight-matched controls given a normal diet. In addition, there was no difference between protein-deficient animals and controls in indices of linear growth (naso-anal and tail length) or fatness (Lee index). We conclude that both growth and reproductive function of male rats show adaptation to long term feeding of a low-protein diet.

Adaptation, Biological↗
PubMedDate not supplied

Sexual maturation in underfed weight-matched rats. A test of the "critical body weight" theory of pubertal timing in males.

A popular current theory proposes that the timing of puberty is related to attainment of a critical level of body weight or body fatness. These critical body weight and critical body fat theories have been studied almost exclusively in females. To explore these theories in males, we tested a corollary of these hypotheses: are male rats of the same weight all at the same level of sexual maturation irrespective of prior growth rate? Male rats growing in body weight at five different rates due to various degrees of underfeeding (beginning at weaning) were sacrificed at body weight milestones of 123 and 279 grams. At the first weight milestone, significant (P less than 0.01) inverse correlations were observed among these weight-matched rats between the preceding rate of body weight growth and prostate weight, seminal vesicle weight, testis weight, serum testosterone, and daily sperm production rate, indicating that the underfed animals were more sexually mature. Testis histology also showed that spermatogenic development increased progressively as the prior rate of body weight growth was reduced. These parameters of sexual maturation tended to correlate inversely with body fatness (i.e., leaner animals were more sexually mature) and directly with body length (i.e., longer animals were more sexually mature). By the second body weight milestone, however, the degree of prior underfeeding exerted little effect on those indices of sexual development. We conclude that the degree of sexual maturation in weight-matched animals with varying previous patterns of body weight growth correlates inversely with body fatness and the rate of body weight growth but correlates directly with body length.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMedDate not supplied

Pituitary-testicular reserve in men with low serum testosterone and normal serum luteinizing hormone.

Men with low serum testosterone levels who do not have elevated serum LH levels are generally thought to have hypothalamic-pituitary dysfunction. To evaluate this concept, seven men with a combination of low serum testosterone and normal serum LH underwent standard tests of hypothalamic-pituitary-testicular reserve. Pituitary reserve, tested with LHRH, showed exaggerated responses in two subjects, low-normal responses in one subject, and normal responses in the remaining four. Testing of hypothalamic-pituitary reserve with clomiphene showed normal gonadotropin responses in six subjects and blunted response in one (the same subject with the low LHRH response). Direct stimulation with hCG showed normal percentage increases in testosterone but low absolute levels, comparable to responses in patients with Klinefelter's syndrome. However, 17-OH-progresterone responses to hCG were lower in these subjects than in either controls or subjects with Klinefelter's syndrome. During follow-up, one subject developed frank primary testicular failure. It was concluded that men with low serum testosterone but normal serum LH are a heterogeneous group, and this pattern occasionally reflects early primary testicular failure rather than hypothalamic-pituitary dysfunction. Standard tests of pituitary-testicular reserve are generally not useful in defining abnormal hormonal output, although measurement of the 17-OH-progesterone response to hCG may improve their diagnostic utility.

17-alpha-Hydroxyprogesterone↗