MON-039 - Atypical Presentation of Acromegaly with Isolated Finger Pain Despite Severe Biochemical Disease

Introduction:

Acromegaly, typically caused by a pituitary somatotroph adenoma, often presents insidiously. The average diagnostic delay is 7-10 years due to the slow progression of somatic changes. While classic features include frontal bossing and macroglossia, subtle musculoskeletal symptoms can be the primary presenting complaint. We present a case of severe biochemical acromegaly where localized finger pain and swelling were the initial manifestations, masking a significantly elevated IGF-1 level.

Case Presentation:

A 45-year-old woman with an 8-year history of prediabetes presented for evaluation of persistent, localized pain and swelling in a single digit of the right hand. Initial workup for inflammatory arthritis was negative. Upon detailed review of systems, she noted subtle "jaw inflammation," shoes fitting tighter without a change in size, and mild blurred vision when using her computer. She denied headaches, galactorrhea, or overt changes in facial features.

Laboratory evaluation revealed an IGF-1 of 935 ng/mL (reference range: 52–328 ng/mL), representing a 2.8-fold elevation above the upper limit of normal. Fasting growth hormone (GH) was 27.86 ng/mL. An oral glucose tolerance test (OGTT) failed to suppress GH, with a nadir of 23 ng/mL. Her A1c had progressed to 6.6%, consistent with new-onset diabetes secondary to GH-induced insulin resistance. Other pituitary axes were intact. MRI identified a pituitary macroadenoma. The patient underwent transsphenoidal resection; pathology confirmed a well-differentiated somatotroph pituitary neuroendocrine tumor (PitNET) with strong GH immunohistochemical staining.

Discussion:

This case highlights two critical clinical pearls. First, musculoskeletal complaints are often the earliest signs of acromegaly but are frequently misattributed to primary joint disease or overuse. Second, there is often a marked discordance between biochemical severity and phenotype. Despite an IGF-1 nearly triple the upper limit of normal and a lack of GH suppression on OGTT, this patient lacked the "classic" acromegalic facies. Weight stability and the absence of overt acral enlargement can provide false reassurance, leading to prolonged morbidity.

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