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Effects of growth hormone and insulin-like growth factor I on testosterone secretion in premature male rats
1Department of Pediatrics, Yamanashi Medical University, Japan.
Insights
Growth hormone (GH) and insulin-like growth factor I (IGF-I) enhance testosterone secretion in premature male rats. These hormones improve testicular responsiveness to gonadotropin stimulation, boosting testosterone production.
Area of Science:
- Endocrinology
- Reproductive Biology
- Pediatric Endocrinology
Background:
- Testosterone production is crucial for male sexual development.
- Growth hormone (GH) and insulin-like growth factor I (IGF-I) play significant roles in growth and development.
- The specific impact of GH and IGF-I on testosterone secretion in premature male rats requires further elucidation.
Purpose of the Study:
- To investigate the effects of GH and IGF-I on testosterone secretion in premature male rats.
- To determine if GH and/or IGF-I administration influences testicular responsiveness to human chorionic gonadotropin (hCG).
Main Methods:
- Forty 3-week-old male rats were divided into four groups: control (saline), GH, IGF-I, and combined GH + IGF-I.
- Subcutaneous administration of treatments occurred daily for one week.
- Serum testosterone responses to hCG loading were assessed.
- Testosterone production by isolated Leydig cells stimulated with hCG was measured.
Main Results:
- Rats treated with GH and/or IGF-I exhibited significantly higher serum testosterone responses to hCG compared to controls.
- Testosterone production by isolated Leydig cells was significantly increased in GH and/or IGF-I treated rats following hCG stimulation.
- No significant differences in testosterone response were observed among the three treatment groups (GH, IGF-I, GH + IGF-I).
Conclusions:
- GH, potentially mediated by IGF-I, enhances testicular responsiveness to gonadotropin stimulation in premature male rats.
- GH and IGF-I promote testosterone production in the testes of young male rats.
- These findings highlight the role of GH/IGF-I axis in early male reproductive development.
Abstract:
Present study was planned to clarify the effects of GH and insulin-like growth factor I (IGF-I) on testosterone secretion using premature male rats. Forty rats were divided four groups. GH, IGF-I, both of them or normal saline solution as control were subcutaneously administered to the rats of each group for seven days from 3-week to 4-week of age. After the treatment, six of each group were used to human chorionic gonadotropin (hCG) loading and four to Leydig cell preparation. Serum testosterone responses to hCG loading were significantly higher in 4-week-old rats treated with GH and/or IGF-I for 1 week than in control rats. However, the responses were similar among three treated groups (GH, IGF-I and both). After one-week treatment with GH and/or IGF-I, isolated Leydig cells were prepared from testes of 4-week-old rats and testosterone production by the stimulation of hCG was examined. Amounts of testosterone production stimulated by hCG were significantly greater in the treated rats than in control rats. These findings suggest that GH mediated by IGF-I promotes the testicular responsiveness to gonadotropin on testosterone production in premature rats.