Insulin-like growth factor I levels during growth hormone (GH) replacement in GH-deficient adults: a gender difference

To evaluate the variation of serum IGF-1 levels during GH replacement and observe gender differences, 29 adults with GH deficiency (mean age 42.5 +/- 10.1 year), were studied. Serum IGF-1 was assessed every 4 weeks during the titration period and afterwards every 3 months of GH therapy. At baseline 77.7% of women and 45.4% of men had serum baseline IGF-1 levels below the lower limit of normal age-related reference range. The time to reach the maintenance dose was lower in men than women (p0.05). There was an increase in IGF-1 levels after one year of GH therapy, significant only in men (p0.01). IGF-1 concentrations were higher in men than women (p0.05), at the 12th and 18th months of GH therapy. GH dose was reduced by 25% in men (p0.01). At the end of the study the mean GH dose was lower in men than in women (p0.05). The factor responsible for these findings is not known, however a possible role of androgens has been suggested.