Continuous subcutaneous pump infusion of somatostatin analogue SMS 201-995 versus subcutaneous injection schedule in acromegalic patients.

Diurnal serum GH patterns were determined in 10 acromegalic patients before treatment, after 3 d continuous s.c. pump infusion and then after 3 d with three equal daily s.c. injections in both instances totalling 100 micrograms/24 h. Subcutaneous injections (33 micrograms) induced impressive suppression of serum GH lasting 3-6 h in eight patients followed by escape to pretreatment values before the next injection. In contrast, continuous infusion resulted in greater and more stable 24 h suppression to the levels reached at the nadir between injections. Suppression of mean 24 h serum GH below 5 ng/ml was achieved by pump treatment in four patients, while two patients had mean values between 5 ng/ml and 10 ng/ml. In four patients occasional or all levels were above 10 ng/ml (24 h average 12.4-102 ng/ml) implying either that adequate suppression by the SMS 201-995, was impossible during the 3 d pump infusion period, or that the dose administered was inadequate. Carbohydrate tolerance was unaffected in either regimen, indicating that reduction in insulin antagonistic hormones balanced inhibition of insulin release. Interestingly, and in contrast to somatostatin, SMS 201-995 did not inhibit TSH release. No untoward effects were observed at the moderate dosage and blood clinical chemistry was unchanged. Fairly constant diurnal serum SMS 201-995 values were obtained during pump infusion, while levels undulated inversely with serum GH during injection treatment. Average diurnal serum somatostatin-C immunoreactivity (all patients) decreased from 496 +/- 129 (mean +/- SD) to 385 +/- 100 ng/ml (P less than 0.003) during pump treatment and did not decrease further during the following 3 d injection treatment (363 +/- 76 ng/ml). The normal adult mean is 179 +/- 40 ng/ml. Computer tomographic (CT) scans of the sellar region were performed in all patients before and after the experimental week. Two patients had extracellular tumours whose size decreased from 8.2 to 4.1 cm3 and from 12.6 to 10.5 cm3. The results demonstrate that superior and stable suppression of GH secretion is obtained during continuous s.c. pump infusion of SMS 201-995.