Endocrine Abstracts

JOINT2796

Introduction: Acromegaly is a neuroendocrine disorder characterized by chronic hypersecretion of growth hormone (GH). Insulin-like growth factor 1 (IGF-1) is currently the primary marker for assessing disease activity and treatment effectiveness due to its strong correlation with GH levels. However, cases with discordant GH and IGF-1 levels pose diagnostic and therapeutic challenges.

Clinical Case Description: At 22 years old, Patients. reported back pain, recurrent fever, skin hyperpigmentation, breast discomfort with nipple discharge, and progressive enlargement of facial features, hands, and feet. Laboratory tests revealed hyperprolactinemia (1,701.0 mIU/l; reference range: 66.0–436.0) and non-elevated IGF-1 (164.0 ng/ml; reference range: 82.0–283.0). Brain MRI identified a pituitary macroadenoma measuring 26×41×34 mm. Treatment with cabergoline 0.5 mg twice weekly was initiated. At 23 years old, despite a normal IGF-1 level (85.4 ng/ml), the patient demonstrated active acromegaly with markedly elevated basal GH (80.0 ng/ml; reference range: 0.02–1.23) and insufficient suppression during an oral glucose tolerance test (OGTT) (minimum GH: 60 ng/ml at 120 minutes). MRI showed tumor progression (32×35×23 mm). The patient was started on long-acting octreotide 20 mg every 28 days. Subsequent assessments revealed persistently elevated GH (26.6 ng/ml) despite a normal IGF-1 (120.9 ng/ml). MRI showed tumor regression (32×29×23 mm), prompting an increase in the octreotide dose to 40 mg. Six months later, the patient underwent transnasal adenomectomy. Postoperatively, maximum GH suppression during OGTT was 0.6 ng/ml at 90 minutes. Immunohistochemical analysis confirmed a sparsely granulated somatotropinoma, with GH expression in tumor cells, Ki-67 <1.0%, strong somatostatin receptor subtype 2 and 5 expression (>80% of tumor cells, IRS-8), and CAM 5.2 expression in fibrous bodies. At 25 years old, laboratory results confirmed persistent disease activity: IGF-1 remained within the normal range (85.7 ng/ml), but GH was elevated (5.1 ng/ml) with inadequate suppression during OGTT (minimum GH: 3.28 ng/ml at 90 minutes). MRI showed only postoperative changes. The patient continued treatment with long-acting octreotide 20 mg daily.

Conclusion: This case highlights the need for an expanded diagnostic approach in acromegaly, particularly in cases with discordant GH and IGF-1 levels. Alongside IGF-1 measurement, GH levels—both basal and during OGTT—should be systematically evaluated to ensure accurate disease monitoring and treatment optimization.