Acromegaly due to ectopic secretion of growth hormone-releasing hormone (GHRH) is rare. Treatment consist of surgical removal of the primary tumour, cytostatic therapy, ‘cold’ or radioactive somatostatin analogue treatment, and medical therapy for acromegaly, if needed.
A 53 year-old female had an ocular lesion noted on a routine optician visit, originally considered to be an ocular melanoma. She had a bronchial carcinoid successfully removed 22 years previously. She had acromegalic features with an enlarged pituitary gland on MRI, but additionally metastatic lesions in her bones, liver and thyroid gland. Elevated GHRH levels (>250x upper-limit-of-normal) suggested a metastatic lung neuroendocrine tumour secreting GHRH. ‘Cold’ and radioactive somatostatin analogue therapy reduced both GHRH and IGF-1 levels, but normalisation of the biochemical markers of acromegaly was only achieved after pegvisomant was introduced. Complete control of IGF-1 was achieved, and this may have hindered the growth of the metastatic lesions as well, as the patient remains well 13 years after the diagnosis of metastatic disease, and 35 years after the original lung operation. A gradual rise in prolactin levels over last 4 years was noted, which is likely due to the prolonged effect of GHRH on prolactin-secreting cells.
The diagnosis of this case applied the law of parsimony from the ‘Ockham’s razor’ principle. We consider that breaking the vicious circle of IGF-1 feeding the metastatic tumour was key for the long-term outcome of this case.