Gender differences in rhGH-induced changes in body composition in GH-deficient adults

Area of Science:

• Endocrinology
• Metabolism
• Body Composition Analysis

Background:

• Recombinant human growth hormone (rhGH) influences body composition in adults with growth hormone deficiency (GHd).
• Previous research indicated sex steroid-dependent gender differences in Insulin-like Growth Factor-I (IGF-I) responsivity to rhGH.

Purpose of the Study:

• To evaluate the effects of rhGH therapy on body composition parameters in GH-deficient adults.
• To specifically investigate gender-based differences in biological responsiveness to rhGH therapy.

Main Methods:

• A 2-year longitudinal study involving 44 women and 33 men with GH deficiency.
• Body composition (total body water, fat-free mass, fat mass) measured by bioimpedantiometry every 6 months.
• rhGH dosage adjusted to achieve age-adjusted normal IGF-I levels.

Main Results:

• Women required significantly higher rhGH doses than men to reach target IGF-I levels.
• Both genders experienced significant increases in total body water and fat-free mass, with greater effects observed in men.
• Fat mass initially decreased more significantly in men, then returned to baseline values after 2 years.
• IGF-I responsivity, total body water, and fat-free mass responsivity to rhGH were significantly higher in men than in women.
• In men, body composition responses relative to IGF-I changes increased over time, suggesting enhanced target organ sensitivity.

Conclusions:

• Gender disparities in IGF-I responsivity to rhGH are associated with differential changes in body composition.
• Men exhibit greater increases in total body water and fat-free mass in response to rhGH replacement therapy compared to women.
• Potential increasing target organ sensitivity to IGF-I over time may explain enhanced body composition responses in men during long-term rhGH therapy.