Twenty-five acromegalic patients were studied during 6 years of treatment with octreotide, with a particular focus on the following parameters: (1) Administration schedule: in 10 patients, continuous subcutaneous (SC) octreotide infusion was compared with injections of octreotide at three dose levels (100, 250, and 1,500 micrograms/24 h) and was found to induce a greater and less-fluctuating 24-hour growth hormone (GH) suppression. (2) Carbohydrate tolerance: average 24-hour blood glucose levels were unaffected by octreotide, regardless of administration schedule. Oral carbohydrate tolerance and intravenous (IV) glucose tolerance were unaffected by continuous octreotide infusion. However, octreotide injection given shortly before the tests reduced carbohydrate tolerance. (3) Thyroid function: octreotide and somatostatin acutely reduce the response of thyroid-stimulating hormone (TSH) to thyrotropin-releasing hormone (TRH). After a few days of treatment, it was demonstrated that octreotide slightly inhibits iodothyronine deiodination and induces a transient reduction in serum triiodothyronine (T3), rapidly compensated for by a persistent slight elevation of serum TSH. (4) Fat absorption was estimated as 24-hour fecal fat content and found to be in the same high-normal range before and after octreotide treatment. Vitamin K and D absorption were unaffected by octreotide. The incidence of gallstone formation was not greater than in the general Danish population, possibly due to the schedule used for octreotide injections. (5) Foot volume was regularly estimated and found to decrease with time, on average by 12% during the first 18 months.(ABSTRACT TRUNCATED AT 250 WORDS)