The Effect of Four Weeks of Supraphysiological Growth Hormone Administration on the Insulin-Like Growth Factor Axis in Women and Men

Measurements of serum insulin-like growth factor I (IGF-I) and related markers are routinely used in the diagnosis and treatment of GH deficiency and excess. The validity of these markers for assessment of exogenous GH exposure in healthy adults is, however, unknown. We therefore conducted a double blind, placebo-controlled GH treatment trial in 99 healthy subjects [49 women and 50 men; mean ± se age, 25.6 ± 0.6 (women)/25.7 ± 0.6 yr (men)]. Blood was collected weekly during a 4-week treatment period (days 1–28), and the subjects were subsequently followed for additional 8 weeks (days 29–84). The treatment arms included: I) 0.1 IU/kg·day GH (n = 30; GH 0.1), II) 0.2 IU/kg·day GH (n = 29; GH 0.2), and III) placebo (n = 40). At baseline no gender-specific differences existed, except that the acid-labile subunit (ALS) levels were higher in females. Serum insulin-like growth factor I (IGF-I) levels in males receiving GH increased significantly through day 42 with no significant difference between the 2 doses....