The Pituitary‐Testicular Axis at Rest and During Moderate Exercise in Males with Diabetes Mellitus and Normal Sexual Function

Abstract

Hormonal studies of pituitary-testicular function in insulin-dependent diabetes mellitus were examined at rest and during moderate exercise to assess whether diabetes per se caused abnormalities of nocturnal penile tumescence and androgen function in men with normal sexual function. The present study compared 10 healthy men and eight men with Type I diabetes mellitus in whom normal sexual function was determined by clinical history. Urinary gonadotropin excretion, semen analysis and diurnal variation of serum glucose, prolactin, testosterone and free testosterone were determined in both groups. In addition, the serum levels of testosterone, free testosterone, prolactin, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured at rest, during 45 minutes of exercise on a bicycle ergometer at 50% of the subjects previously determined maximal oxygen uptake (VO2 max) and during a 30-minute recovery period. Nocturnal penile tumescence and parameters of semen analysis were similar in both groups. Urinary FSH excretion and serum FSH were higher (P less than or equal to 0.01) in the diabetic subjects while urinary LH excretion was similar. Diurnal variation of serum prolactin, testosterone and free testosterone were similar in both groups. Exercise produced a significant (P less than or equal to 0.01) increase in maximal free and total testosterone in both groups without changes in serum FSH or LH. Prolactin increased significantly (P less than or equal to 0.01) during exercise in the diabetic group only. We conclude that, for the most part, the pituitary-testicular axis and nocturnal penile tumescence under basal conditions and the pituitary-testicular axis during moderate exercise are similar in healthy males and insulin-dependent diabetic males with normal sexual function.

Semen Characteristics and Diabetes Mellitus: Significance of Insulin in Male Infertility

“…Freetestosterone plasma levels are lower in impotent diabetics than in those who are not impotent or in normal men [3, 6, 271. These findings have not been confirmed [28,35,391.…”

“…The response of FSH to stimulation with exogenous gonadatropin-releasing hormone (GnRH) in diabetic subjects may be normal [7,9,11,14,32, 391, below normal [41], or exaggerated [20,241. A normal response of LH to stimulation with exogenous GnRH has been reported [14, 321, as has a decreased response [2, 9, 35, 39, 411. Plasma testosterone concentrations are similar to [2,14,19,20,24,28,31,39, 401 or lower than [15, 31 those in normal men. The response of testosterone to human chorionic gonadotropin (hCG) may be normal [lo] or below normal [2, 141.…”

“…Studies on the ejaculates of patients with diabetes mellitus have revealed a decrease in semen volume [4,161 and sperm motility and velocity [4,16,22,371 and an increase in the number of sperm with abnormal morphology [4]. However, sperm density does not usually differ from that observed in healthy men 14,5,16,22,28,31,381. The diabetic state disturbs human testicular steroidogenesis as a result of dysfunction of the hypothalamus, hypophysis, or Leydig cells [23].…”

“…The serum and urinary gonadotropins may be normal [7,9,11,19,20,28,32,35,391 or low [34] or have high-follicle-stimulating-hormone (FSH) levels [16,20,24,281 or high-LH levels [2,6,7,161. The response of FSH to stimulation with exogenous gonadatropin-releasing hormone (GnRH) in diabetic subjects may be normal [7,9,11,14,32, 391, below normal [41], or exaggerated [20,241.…”

Gonadal function in men with chronic illness

“…Testosterone levels were shown to be low in men with diabetic ketoacidosis and rose with recovery, presumably secondary to the effects of a severe illness (Semple et al, 1988). A study comparing healthy type 1 diabetic men with normal controls all of whom had no reported sexual dysfunction, showed that there were no significant differences between the two groups in terms of pituitary-testicular axis during moderate exercise and at rest (Murray et al, 1988). An association between low testosterone levels and insulin resistance in type 2 diabetes has been suggested and insulin levels have been shown to correlate inversely with testosterone levels in men with diabetes (Andersson et al, 1994).…”