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Sex hormone-binding globulin and female reproductive function
N Botwood1, D Hamilton-Fairley, D Kiddy
1Department of Obstetrics and Gynaecology, Imperial College of Science, Technology and Medicine, St Mary's Hospital Medical School, London, U.K.
Summary
Nutritional factors significantly impact sex hormone-binding globulin (SHBG) levels in women. Weight loss, particularly calorie restriction, improves SHBG and reduces testosterone in women with PCOS.
Area of Science:
- Endocrinology
- Reproductive Health
- Metabolic Disorders
Background:
- Sex steroids influence sex hormone-binding globulin (SHBG), but nutritional factors are increasingly recognized as key regulators in women.
- SHBG levels correlate negatively with body mass index (BMI) and central adiposity.
- Polycystic ovary syndrome (PCOS) involves obesity, hyperandrogenism, and hyperinsulinemia, with insulin potentially mediating weight-related SHBG changes.
Purpose of the Study:
- To investigate the relationship between BMI, insulin, and SHBG in women, particularly those with PCOS.
- To understand the clinical significance of weight-related SHBG suppression in PCOS.
- To evaluate the impact of dietary interventions on SHBG, insulin, and androgen levels.
Main Methods:
- Correlational analysis of SHBG with BMI, central adiposity, and insulin levels (fasting and glucose-stimulated).
- In vitro studies on insulin's effect on SHBG synthesis and secretion by hepatocytes.
- Comparative analysis of SHBG, testosterone, and free testosterone in lean versus obese women with PCOS.
- Intervention study involving calorie restriction versus an isocaloric, low-fat diet.
Main Results:
- Serum SHBG is inversely correlated with insulin levels, suggesting insulin's inhibitory effect on SHBG.
- The interrelationship between BMI, insulin, and SHBG differs between women with PCOS and normal subjects.
- Obese women with PCOS exhibit lower SHBG and higher free testosterone compared to lean counterparts.
- Calorie restriction reduces insulin, increases SHBG, and lowers free testosterone; a low-fat diet has no significant effect.
Conclusions:
- Weight reduction is crucial for managing anovulation and hirsutism in obese, hyperandrogenemic women with PCOS.
- Insulin plays a significant role in regulating SHBG, particularly in the context of obesity and PCOS.
- Dietary interventions, specifically calorie restriction, can positively modulate SHBG and androgen levels in PCOS.