Influence of short-term fasting on the pituitary-testicular axis in normal men.
To investigate whether short-term fasting affects serum testosterone (T) in normal subjects, 10 healthy men of normal weight were studied on two occasions: after an overnight fast (8 h), and after an additional 48 h of fasting. Blood glucose declined by 22 +/- 3% between the tests (p less than 0.001). Basal serum T fell from 8.7 +/- 0.7 to 5.7 +/- 0.8 micrograms/l (p less than 0.01), and LH from 6.9 +/- 0.8 to 5.0 +/- 0.7 U/l (p less than 0.01). Serum estradiol (E2) and FSH remained unaffected. To explore possible mechanisms behind the decreased basal release of T and LH, 9 small doses of glucose were given orally at regular intervals during a 56-hour fast to 9 additional normal men to maintain blood glucose levels. These men did not experience a fall in serum T or LH. Six additional normal men were given 50 micrograms GnRH intravenously after an overnight fast, and after a fasting period of 56 h. No acute increase in T was seen after the overnight fast, but after the 56-hour fast GnRH raised serum T by 55 +/- 14% (p less than 0.02). Moreover, fasting augmented the GnRH-induced LH response by 64 +/- 15% (p less than 0.02. These results imply that: short-term fasting exerts inhibitory influence on Leydig cell function via a mechanism which might involve a reduced hypothalamic and/or pituitary stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004958:Estradiol / Q000097:blood; D005215:Fasting; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
D001786:Blood Glucose; D010906:Pituitary Hormone-Releasing Hormones; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone