Effect of 4 weeks of octreotide treatment on prolactin, thyroid stimulating hormone and thyroid hormones in acromegalic patients. A double blind placebo-controlled cross-over study.

We aimed to test the hypothesis, that octreotide has a suppressive effect on unstimulated and TRH-stimulated PRL levels in both normo- and hyperprolactinaemic acromegalic patients, and besides to evaluate the effect of octreotide on unstimulated TSH and thyroid hormones. The present study is a doubleblind placebo-controlled cross-over trial; the 12 acromegalic patients were treated with octreotide or placebo (300 micrograms/d) for 4 weeks separated by a 12 weeks washout period. Before and after each 4 weeks period a TRH-test (200 micrograms iv) was performed and serum GH and PRL levels were determined. Serum TSH and thyroid hormones were determined after 0, 2, 3, and 4 weeks. In the whole group unstimulated PRL levels were 18 micrograms/l +/- 5 before and 7 micrograms/l +/- 1 during octreotide treatment (p < 0.01). The PRL lowering effect of octreotide was significantly more pronounced in hyperprolactinemic patients compared to normoprolactinaemic patients (p < 0.05). Patients with the highest pretreatment PRL levels had the most pronounced percentage suppression of unstimulated PRL levels during octreotide treatment. Eight out of 12 patients had a TRH-stimulated PRL response > or = 100%, both during placebo and octreotide treatment, but in the group as a whole maximal TRH-stimulated PRL levels were suppressed during octreotide treatment, PRL levels were 50 micrograms/l +/- 20 before and 18 micrograms/l +/- 3 during octreotide treatment (p < 0.05). Unstimulated GH levels were 48 mU/l +/- 15 before and 13 mU/l +/- 2 during octreotide treatment (p < 0.01). Serum total T3 was significantly reduced during octreotide treatment (p < 0.05); serum TSH, total T4 or free T4 index were not significantly changed during treatment. We conclude that patients with acromegaly and hyperprolactinemia will normalize PRL levels during 4 weeks of octreotide treatment and octreotide will reduce total T3 levels in acromegalic patients.