Abstract
Objective: In the medical treatment of acromegaly different factors are influencial; among these the impact on growth hormone binding protein (GHBP) has not been clarified.
Design: Twenty acromegalic patients and nineteen age- and gender-matched normal subjects participated in this study. The patients were treated for 21 months with depot long-acting microsphere-enclosed octreotide (Sandostatin-LAR). Previously, all the patients were treated s.c. with octreotide t.i.d. After a 2-week wash-out period (baseline) the patients received the first i.m. injection of the long-acting octreotide. The first two injections were administered at 60-day intervals; thereafter the injections were at 28-day intervals.
Methods: The levels of GHBP, complexed GHBP, growth hormone (GH) and insulin-like growth factor-I (IGF-I) were determined in fasting serum samples.
Results: In the 2-week wash-out period GHBP levels decreased from 1·13 ± 0·17 to 0·92 ± 0·15 nmol/l (P < 0·05). During the 21-months treatment, GHBP increased again to 1·10 ± 0·16 nmol/l. In the age- and gender-matched control group GHBP levels were significantly higher at all times (1·95 ± 0·21 nmol/l, P(all) < 0·02). Mean levels of 8-h GH decreased from 12·6 ± 2·58 μg/l at baseline to 1·97 ± 0·20 μg/l after 21 months of treatment (P < 0·05). Mean 8-h GH levels were unchanged during long-acting octreotide treatment compared with levels during s.c. treatment (1·97 ± 0·20 μg/l and 1·90 ± 0·20 μg/l respectively). In fasting blood samples GH-complexed GHBP ranged from 13·8 ± 2·4% (9 months) to 25·4 ± 4·5% (baseline) of total GHBP. Serum IGF-I increased from 367 ± 45 to 764 ± 80 μg/l (P < 0·05) during the 2-week wash-out period and decreased to 290 ± 35 μg/l (P < 0·05) after 21 months of treatment with long-acting octreotide. IGF-I levels after 21 months were significantly lower than during s.c. octreotide treatment (P < 0·05).
Conclusion: Serum GHBP levels are similar during treatment with long-acting octreotide as compared with regular octreotide. Furthermore, significant changes in GHBP can occur within 2 weeks. Finally, in addition to the lowering effect on GH levels, the induced increase in GHBP levels may imply a further advantage in octreotide treatment of acromegaly, circulating GH bound to GHBP may less readily reach the tissues.
European Journal of Endocrinology 136 61–66
