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J Clin Endocrinol Metab. 2018 Dec 1;103(12):4419-4427. doi: 10.1210/jc.2018-00755.

Aromatized Estrogens Amplify Nocturnal Growth Hormone Secretion in Testosterone-Replaced Older Hypogonadal Men.

Author information

1
Department of Internal Medicine, Section of Endocrinology and Metabolism, Leiden University Medical Center, Leiden, Netherlands.
2
Endocrine Research Unit, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota.
3
Department of Primary Care Internal Medicine, Mayo Clinic, Rochester, Minnesota.
4
Division of Endocrinology, Mayo Clinic, Rochester, Minnesota.
5
Department of Internal Medicine, Tulane University Health Sciences Center, New Orleans, Louisiana.

Abstract

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.

PMID:
30032193
PMCID:
PMC6212797
[Available on 2019-12-01]
DOI:
10.1210/jc.2018-00755
[Indexed for MEDLINE]

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