Changing patterns of insulin-like growth factor-I and glucose-suppressed growth hormone levels after pituitary surgery in patients with acromegaly.

OBJECT: According to a recent consensus statement on the treatment of acromegaly, its biochemical cure is defined as the normalization of age- and sex-adjusted insulin-like growth factor (IGF)-I levels and the suppression of growth hormone (GH) by glucose to lower than 1 ng/ml. The present study was prompted by the clinical observation that many cases of acromegaly can be considered cured according to one criterion but not others at different moments in a patient's postoperative course.
METHODS: Fifty-three patients with acromegaly (30 women and 23 men) harboring nine microadenomas and 44 macroadenomas were evaluated after surgery by assessing age- and sex-adjusted IGF-I levels as well as glucose-suppressed GH levels. Fifty of these patients were studied more than once during follow up. Acromegaly was categorized as cured if the patient's IGF-I level was normal and their glucose-suppressed GH level was lower than 1 ng/ml; the disease was considered to be active if the patient's IGF-I level was high and the GH nadir was higher than 1 ng/ml following administration of glucose. Discordant categories of the disease were found in patients with high IGF-I levels and a GH nadir lower than 1 ng/ml after glucose administration and in those with normal IGF-I levels and a GH nadir higher than 1 ng/ml after glucose intake. At the first postoperative biochemical evaluation (1-3 months), 34% of patients harboring macroadenomas were classified as having been cured of acromegaly, 39% as having the active disease, and 27% as having the discordant form of the disease. When last evaluated (> or = 12 months postoperatively), the percentage of patients with the discordant form dropped to 14% and the proportion of cases cured and active was 44% and 41%, respectively. Of the nine patients with microadenomas, 44.4% were cured of acromegaly, 33.2% had the active disease, and 22% had the discordant variety on first evaluation. Twelve months or longer after transsphenoidal surgery, 55.5% of cases were cured, 11.1% were active, and 33% were discordant. In most cases, the discordant variety developed because of a persistently elevated level of IGF-I, followed by an incompletely suppressed GH level. Nineteen patients (38%) modified their biochemical category. In 15 of these patients this change in category was due to a change in IGF-I levels, becoming normal in 12 patients and rising to above normal range in three. A tumor remnant was demonstrated on magnetic resonance images in only four of these 19 patients.
CONCLUSIONS: The authors conclude that the discordance rate between the biochemical markers that define cure in acromegaly is higher than previously reported, and the biochemical status assigned to a patient early in the postoperative course is very likely to change later, particularly when initially discordant.