Related Experiment Videos
GH responsiveness varies during the menstrual cycle.
Helena K Gleeson1, Stephen M Shalet
1Department of Endocrinology, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX, UK. Helena.Gleeson@christie-tr.nwest.nhs.uk
European Journal of Endocrinology
|December 3, 2005
Summary
Fluctuating estrogen levels in women affect growth hormone (GH) sensitivity, reducing the body's response to GH during the menstrual cycle. This finding suggests potential implications for hormone replacement therapy in women with GH deficiency.
Area of Science:
- Endocrinology
- Reproductive Biology
Background:
- The growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis is influenced by estrogen.
- While estrogen enhances central GH secretion, its effect on IGF-1 levels is less clear, with evidence suggesting reduced GH sensitivity at high exogenous estrogen doses.
Purpose of the Study:
- To investigate whether fluctuating endogenous estrogen levels during the menstrual cycle modify GH sensitivity in women.
- To assess GH sensitivity across different phases of the menstrual cycle using the IGF-1 generation test.
Main Methods:
- Nine women with regular menstrual cycles underwent an IGF-1 generation test involving a subcutaneous injection of 7 mg GH.
- Measurements of IGF-1, IGFBP-3, and ALS were taken at baseline and 24 hours post-injection during the early follicular (EF), periovulatory (PO), and midluteal (ML) phases.
Main Results:
- Estradiol levels were significantly lower in the EF phase compared to PO and ML phases.
- Baseline IGF-1 levels were lower in the EF phase, but the increment in IGF-1 after GH administration was higher in the EF phase compared to later phases.
Conclusions:
- Increased endogenous estrogen levels from midcycle onward are associated with modestly elevated baseline IGF-1 and reduced GH sensitivity, indicated by a lower IGF-1 increment.
- These findings may have clinical implications for managing women with isolated GH deficiency and regular menstrual cycles on fixed GH doses, warranting further investigation.