When Appearances Deceive: A Silent Somatotroph Macroadenoma Presenting With Acromegaloid Features and Paradoxically...

Silent somatotroph adenomas are uncommon pituitary neuroendocrine tumours (PitNETs) of the PIT1 lineage that express growth hormone (GH) immunohistochemically but without biochemical evidence of acromegaly. We report the case of a 32-year-old male patient referred with recurrent epistaxis, headache, right-sided diplopia, and third cranial nerve palsy. Clinical examination revealed acromegaloid features including frontal bossing, spade-like hands, and coarse facies, which were strongly suggestive of longstanding GH excess. However, preoperative insulin-like growth factor-1 (IGF-1) was paradoxically low at 13.1 nmol/L (reference range 15.5-33.1 nmol/L), creating a striking clinical-biochemical discordance. MRI demonstrated a giant sellar and suprasellar mass with chiasmal compression, right cavernous sinus invasion, and extension into the paranasal sinuses. The patient underwent endoscopic transsphenoidal resection. Neuropathology confirmed a densely granulated PIT1-lineage somatotroph adenoma with scattered GH positivity, diffuse Pit-1 staining, and a Ki-67 index below 2%. This case highlights the diagnostic challenge posed by silent somatotroph adenomas, underscores the limitations of biochemical assessment alone, and reinforces the essential role of histopathology and immunohistochemistry in establishing a definitive diagnosis. Long-term endocrine and neurosurgical surveillance is strongly recommended given the potential for phenotypic transformation to a functioning acromegaly syndrome.