Dexamethasone suppresses sex-hormone binding globulin

Area of Science:

• Endocrinology
• Reproductive Medicine

Background:

• Polycystic ovarian disease (PCOD) is characterized by androgen excess, with the source often investigated using dexamethasone suppression (DEX-S).
• The precise mechanism by which DEX-S influences androgen levels, particularly its effect on sex-hormone binding globulin (SHBG), remains incompletely understood.

Purpose of the Study:

• To investigate the hypothesis that dexamethasone (DEX) inhibits the synthesis or secretion of SHBG.
• To examine the effects of a 14-day DEX-S regimen on various hormones, including androgens and SHBG, in women with PCOD.

Main Methods:

• Fourteen women with PCOD (both obese and nonobese) and three healthy volunteers received DEX for 14 days.
• Plasma levels of total testosterone, free testosterone, androstenedione, dehydroepiandrosterone sulfate, luteinizing hormone, follicle-stimulating hormone, cortisol, and SHBG were measured using radioimmunoassay before and after DEX treatment.

Main Results:

• DEX administration significantly suppressed SHBG levels (P < 0.01).
• Obese participants exhibited significantly lower baseline SHBG levels compared to nonobese participants (P < 0.01).
• While most androgens were suppressed by DEX, androstenedione levels increased post-treatment in 6 out of 14 subjects, consistent with SHBG suppression.

Conclusions:

• Dexamethasone suppression therapy demonstrably reduces SHBG levels.
• The observed decrease in SHBG may contribute to the mechanism by which DEX-S influences androgen dynamics in PCOD.
• Obesity is associated with lower SHBG levels, independent of DEX treatment.