Endocrine Abstracts

Introduction: Remission after transsphenoidal surgery in patients with acromegaly is confirmed by biochemical assays of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Although their levels are usually closely correlated, discordant results of these tests have been noted, making the follow-up of acromegaly patients particularly challenging.

Case report: We present the case of a 35 year old female diagnosed with acromegaly at the age of 32 years. At the time of diagnosis a 20.9 x 17 x 16 mm macroadenoma was found on pituitary MRI. IGF-1 was 408 ng/ml (normal age and sex-matched values 115-307), serum nadir GH during a 75 g oral glucose tolerance test (OGTT) was 5.61 ng/ml and prolactin levels were 51.92 ng/ml (normal values <26.53). She underwent endoscopic transsphenoidal surgery, with immunohistochemistry analysis revealing a mixed somatotroph-lactotroph pituitary adenoma, with a Ki 67 index of 6%. Analysis of GPR101 and AIP genes mutations was negative. She developed transient postoperative SIADH with hyponatermia (sodium values of 118 mEq/l). Postoperative evaluation 3 months after surgery showed no tumor remnant on pituitary MRI, normal IGF-1 [257 pg/ml (normal age and sex-matched values 115-307)], but a lack of inhibition of GH after OGTT (nadir values of 0.733 ng/ml). At this moment the chosen approach was biochemical evaluation every 6 months and annual pituitary MRI. For the next two and a half years the patient had the same biochemical profile of normal IGF-1 but unsuppressed GH during OGTT and no tumor remnant visible on MRI. However, at the last evaluation in January 2022 we found elevated levels of IGF-1 (341.3 ng/ml, 1.23 x upper limit of normal), serum nadir GH during OGTT of 2.55 ng/ml and no changes on pituitary MRI. Taking into account the marginally elevated IGF-1 and the patient’s desire to undergo an in-vitro fertilization procedure in the near future, we opted for initiation of therapy with cabergoline until pregnancy is obtained and we are considering referring the patient for a ¹¹C-methionine PET/CT for accurate localization of a potential residual/recurrent pituitary adenoma.

Conclusions: Management of surgically treated acromegaly patients with discordant GH and IGF-1 values is a challenge. Close biochemical evaluation is needed and an individualized approach is warranted, but further studies are needed to asses the risk of disease recurrence and the impact on the patient’s quality of life.