Endocrine Abstracts

Background: Growth hormone (GH) is known to have stimulatory effects on bone tissue through a complex interaction of GH, IGF-1 and IGFBPs. The gonadal status is also thought to influence bone metabolism. Bone mass in patients with acromegaly reflects the long-time effects of GH excess on bone. However, data on bone status in acromegaly have been conflicting.

Objective: The object of the study was to examine the impact of chronic GH excess on bone mass and metabolism, with special respect to gonadal status.

Methods: Consent was given from the local ethical committee. Of the 73 patients (40 women) with active acromegaly included, none had received somatostatin analogue or radiation therapy. Gonadal status was defined by menstrual history and hormonal replacement therapy in women, and calculated biotestosterone levels in men. Bone mass was examined by DEXA, and serum IGF-1, IGFBP3, GH, osteocalcin and CrossLaps were measured by immunoassay. A reference population (n=40) matched by sex, age and BMI was used.

Results: Osteocalcin and CrossLaps were significantly higher in the acromegalic group (P<0.001). BMC of all segments were unaltered, whereas the area of several segments was significantly increased. Nine men and 19 women were hypogonadal. In both men and women markers of bone metabolism, BMC and area of all segments were unaltered compared to the eugonadal acromegalic group. In multiple regression analysis age and sex, but not gonadal status, were significant determinants of total BMC. IGF-1, but not GH, was significantly correlated to total BMC both in the normal and the acromegalic group.

Conclusion: No differences in bone mass were found in the acromegalic group compared to a matched reference population; however, markers of bone turnover were increased. In both groups IGF-1 were correlated to BMC. Gonadal status had no impact on bone metabolism or mineralization in this large study.