Gender differences in the effects of long term growth hormone (GH) treatment on bone in adults with GH deficiency

We recently observed that among patients with GH deficiency due to adult-onset hypopituitarism, men responded with a greater increase in serum levels of insulin-like growth factor I (IGF-I) and biochemical markers of bone metabolism than women when the same dose of recombinant human GH (rhGH) per body surface area was administered for 9 months. In the present study 33 of the 36 patients in the previous trial (20 men and 13 women) continued therapy for up to 45 months. The dose of rhGH was adjusted according to side-effects and to maintain serum IGF-I within the physiological range. This resulted in a significant dose reduction in the men; consequently, the women received twice as much rhGH as the men (mean +/- SD, 1.9 +/- 1.1 vs. 1.0 +/- 0.6 U/day; P < 0.01). The increases in serum IGF-I levels and serum biochemical markers of bone metabolism were similar in men and women with these doses. The total bone mineral content (BMC) was increased after 33 and 45 months of treatment up to 5.1% (P = 0.004 and 0.0001). Bone mineral density (BMD), BMC, and the area of the femoral neck and the lumbar spine were also significantly increased after 33 and 45 months of treatment. When analyzed by gender, total body BMC, femoral neck BMD and BMC, and spinal BMC were significantly increased in males, but not in females (P < 0.05-0.01). In conclusion, rhGH treatment continued to have an effect on bone metabolism and bone mass for up to 45 months of therapy. The changes in bone mass were greater in the men, although they received lower doses of rhGH than the women. The results indicate that the sensitivity to GH in adult patients with GH deficiency is gender dependent.