Ectopic Acromegaly Secondary to Bronchial Tumour: A Case Report of Rare Occurrence.

Introduction: Acromegaly is caused due to the unregulated and sustained overproduction of growth hormone (GH). The majority of the cases are caused by autonomous secretion of GH from anterior pituitary tumours. Nonetheless, in <1% of the cases, the cause of autonomous secretion is secondary to ectopic GH-releasing hormone (GHRH) production. Bronchial carcinoids are the most common cause of ectopic GHRH production.

Case Description: A 32-year-old female presented to the clinic with a history of cough, haemoptysis and undocumented weight loss for 4 years. Initial workup showed a large right main stem endobronchial mass. Transbronchial biopsy of the mass revealed a Grade I neuroendocrine tumour (NET). During NET workup, a large sellar mass was incidentally found on cross-sectional imaging. The hormonal profile revealed markedly elevated insulin-like growth factor-1 (IGF-1) and mildly raised prolactin. The magnetic resonance imaging (MRI) brain study revealed pituitary macroadenoma measuring 2 cm × 1.2 cm × 1.5 cm. The patient underwent bronchial carcinoid tumour resection, which led to normalisation of serum IGF-1 and GH response to an oral glucose tolerance test. Subsequent MRI brain revealed complete resolution of previously noted sellar mass.

Practical Implications: This case highlights the importance of differentiating acromegaly secondary to pituitary adenoma and ectopic acromegaly. This case emphasises the importance of keeping rare entities in the differential while assessing patients with pituitary macroadenoma.