LONG-TERM EFFECTS OF OCTREOTIDE ON MARKERS OF BONE METABOLISM IN ACROMEGALY - EVIDENCE OF INCREASED SERUM PARATHORMONE CONCENTRATIONS

The effects of octreotide on biochemical markers of bone turnover were evaluated in patients with active acromegaly. Serum GH, IGF-I and ser um and urinary markers of bone metabolism were measured before and aft er 4 months of treatment in 27 patients (short-term treatment) and aft er 12 and 24 months of treatment in 15 patients (long-term treatment). In the short-term, octreotide significantly decreased the levels of s erum GH, IGF-I, calcium, osteocalcin, carboxyterminal propeptide of ty pe I collagen and alkaline phosphatase plus urinary excretion of calci um. Short-term treatment significantly increased serum parathormone le vels (before treatment 30.1+/-9.57 and at 4 months 46.1+/-24.98 ng/L, p<0.001) and urinary excretion of phosphate; urinary excretion of hydr oxyproline was unchanged. The same results were observed during long-t erm treatment, except that there was no significant difference of sei um calcium and alkaline phosphatase levels before and after treatment. Parathormone concentrations were still higher at 24 months compared w ith those prior to treatment (before treatment 31.9+/-9.74 and at 24 m onths 44.9+/-21.18 ng/L, p<0.05). The changes of most bone markers dur ing octreotide therapy can be explained by the decrease of serum GH an d IGF-I concentrations. On the other hand, the rise of parathormone co ncentrations suggests that octreotide has ulterior and long-standing a ctions on calcium homeostasis: intestinal malabsorption of calcium due to the octreotide could contribute to this secondary hyperparathyroid ism. The clinical consequences of these alterations of bone metabolism need to be further clarified. (C) 1997, Editrice Kurtis.