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The known interactions between the somatotropic and hypothalamic‐pituitary‐gonadal (HPG) axes have not been well delineated in older individuals. Aging‐associated decline in insulin like growth factor‐1 (IGF‐1) levels has been proposed to play a role in reproductive senescence in animals. However, the effects of GH on LH secretion are unknown in older individuals. Our objective was to determine whether GH modulates LH secretion or levels of sex steroids (SS) in healthy older (ages 65–88 years) men (n = 24) and women (n = 24) with low‐normal plasma IGF‐1 levels. In a double‐masked, placebo‐controlled (n = 24), randomized study, we evaluated the effects of GH (n = 24, 20 μg/kg sc 3×/week) for 26 weeks on nocturnal LH secretory dynamics [(8 pm to 8 am, Q20) min sampling and analyzed by multiparameter deconvolution algorithm]. Indices of LH secretion [frequency, mass per burst, pulsatile production rate, and approximate entropy (ApEn)] and fasting serum IGF‐1, SHBG, and SS (TT, fT, or E2) were measured. At baseline, all indices of LH secretion (frequency, mass per burst, pulsatile production rate) were inversely (P

Pancreatic β ‐cell dysfunction because of reduced β ‐cell mass and function is a primary determinant in the progression of diabetes. Increase in β ‐cell mass and compensatory hyperinsulinaemia is frequently associated with insulin‐resistant states. Although the humoral factors mediating this compensatory response are unknown, serpinB1, a protease inhibitor, has recently been proposed to be one such factor. In this study, we examine the relationships between plasma serpinB1, insulin sensitivity, and pancreatic β ‐cell function in non‐diabetic individuals. 117 subjects (women, n = 50, men, n = 67; age= 37.6 ± 10.8; BMI=31.1 ± 7.7 kg/m2) underwent an insulin‐modified frequently sampled intravenous glucose tolerance test (FSIVGTT) at the NIH Clinical Research Center. Acute insulin response (AIR) and insulin sensitivity index (SI) were obtained from the FSIVGTT with MINMOD analysis. The Quantitative Insulin Sensitivity Check Index (QUICKI) was calculated from fasting insulin and glucose values. Plasma serpinB1 levels were measured using an ELISA assay. Simple linear correlation analyses were performed to evaluate the relationship between serpinB1 and measures of insulin sensitivity and β ‐cell function. Circulating serpinB1 levels were unrelated to age, sex, race, BMI, or percent body fat. SI but not AIR significantly correlated with circulating serpinB1 levels ( r = 0.23, P