Long-term effect of 90Y pituitary implantation in acromegaly

This report examines the long-term trends in GH levels and pituitary function in a group of 38 acromegalic patients who were selected insofar as we were able to follow them up for more than 10 years after a single dose of 90Y interstitial pituitary irradiation as the sole treatment. Mean serum GH had fallen from 106 to 24 mIU/l within 3-6 months and then slowly declined to 4 mIU/l after 10 years. GH levels of less than or equal to 5 mIU/l during a 50 g oral glucose tolerance test were obtained in 8% of patients at 3-6 months and in 18% at 1 year, the cumulative percentage increasing to 53% at 10, and 76% at 14 years. The percentage of patients requiring hormone replacement therapy rose from nil pre-implant to 16% by 3-6 months, and then slowly increased to 39% by 14 years. Serial coned radiographs of the pituitary fossa were available for 32 patients. By 10 years, 16 showed thickening of the dorsum sellae and/or reduction of at least one diameter by 3 mm. Concerning symptoms, all 29 patients whose GH level fell to less than or equal to 5 mIU/l showed improvements, 22 becoming asymptomatic. Seven patients with lesser falls in GH levels (from a mean of 193 to a mean of 15 mIU/l) all improved, one becoming asymptomatic. Two showed no variation. These results show that 90Y pituitary implants have a cumulative effect over the years in inducing remission and hypopituitarism in acromegalic patients, the early decline in GH levels being swifter than from other forms of irradiation.