TY - JOUR
T1 - Aromatized Estrogens Amplify Nocturnal Growth Hormone Secretion in Testosterone-Replaced Older Hypogonadal Men
AU - Roelfsema, Ferdinand
AU - Yang, Rebecca J.
AU - Takahashi, Paul Y.
AU - Erickson, Dana
AU - Bowers, Cyril Y.
AU - Veldhuis, Johannes D.
N1 - Publisher Copyright:
© 2018 Endocrine Society.
PY - 2018
Y1 - 2018
N2 - Context: Testosterone (T) increases GH secretion in older men with a relative lack of T, in hypogonadal men of all ages, and in patients undergoing sex reassignment. The role of estradiol (E2) in men is less well defined. Objective: To assess the contribution of aromatization of T to spontaneous nocturnal and stimulated GH secretion. Participants: Four groups of healthy older men (N = 74, age range 57 to 77 years) were studied. The gonadotropic axis was clamped with the gonadotropin-releasing hormone antagonist degarelix. Three groups received T and one group placebo addback. Two T-replaced groups were treated with anastrozole (an aromatase inhibitor) and either placebo or E2 addback. Main Outcome Measures: Ten-minute GH concentration profiles were quantified by deconvolution analysis, after overnight (2200 to 0800 hours) sampling, and after combined IV injection of GHRH (0.3 μg/kg) and GHRH-2 (0.3 μg/kg) and withdrawal of a 2-hour somatostatin infusion (1 μg/kg/h). Results: E2 addback during aromatase inhibition increased basal (P = 0.046), pulsatile (P = 0.020), and total (P = 0.018) GH secretion by 60% to 70%. E2 did not potentiate GH secretory stimuli. Logarithmically transformed pulsatile GH secretion correlated strongly and positively with concurrent E2 concentrations overall (P = 0.028) and under anastrozole treatment (P = 0.005). Conclusion: E2 administration in older men transdermally stimulates overnight pulsatile GH secretion. The exact site of E2 action cannot be ascertained from these experiments but may include hypothalamic loci involved in GH regulation, especially because GH secretagogue effects on somatotrope pituitary cells were not affected.
AB - Context: Testosterone (T) increases GH secretion in older men with a relative lack of T, in hypogonadal men of all ages, and in patients undergoing sex reassignment. The role of estradiol (E2) in men is less well defined. Objective: To assess the contribution of aromatization of T to spontaneous nocturnal and stimulated GH secretion. Participants: Four groups of healthy older men (N = 74, age range 57 to 77 years) were studied. The gonadotropic axis was clamped with the gonadotropin-releasing hormone antagonist degarelix. Three groups received T and one group placebo addback. Two T-replaced groups were treated with anastrozole (an aromatase inhibitor) and either placebo or E2 addback. Main Outcome Measures: Ten-minute GH concentration profiles were quantified by deconvolution analysis, after overnight (2200 to 0800 hours) sampling, and after combined IV injection of GHRH (0.3 μg/kg) and GHRH-2 (0.3 μg/kg) and withdrawal of a 2-hour somatostatin infusion (1 μg/kg/h). Results: E2 addback during aromatase inhibition increased basal (P = 0.046), pulsatile (P = 0.020), and total (P = 0.018) GH secretion by 60% to 70%. E2 did not potentiate GH secretory stimuli. Logarithmically transformed pulsatile GH secretion correlated strongly and positively with concurrent E2 concentrations overall (P = 0.028) and under anastrozole treatment (P = 0.005). Conclusion: E2 administration in older men transdermally stimulates overnight pulsatile GH secretion. The exact site of E2 action cannot be ascertained from these experiments but may include hypothalamic loci involved in GH regulation, especially because GH secretagogue effects on somatotrope pituitary cells were not affected.
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U2 - 10.1210/jc.2018-00755
DO - 10.1210/jc.2018-00755
M3 - Article
C2 - 30032193
AN - SCOPUS:85056056581
SN - 0021-972X
VL - 103
SP - 4419
EP - 4427
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 12
ER -