Undiagnosed Acromegaly in a Hyperthyroid Diabetic
James Burn, Chong Lim, Agnieszka Falinska, Rashmi Kaushal
A 73 year-old diet-controlled diabetic lady was referred by her GP in January 2007 with persistently deranged thyroid function. She was clinically euthyroid with a T4 of 7 and Low TSH. Physical examination revealed an enlarged thyroid but no discrete nodules. A subsequent technicium scan revealed a toxic mutinodular goitre and she was commenced on 5mg of Carbimazole. When reviewed in clinic 3 months later she was noted to have doughy hands, drumstick fingers and course facial features when reviewed with old photographs. Further questioning revealed increasing difficulty wearing rings (for which she had started diuretics) and she was no longer able to fit a hat bought some years previously. She had also suffered frontal headaches periodically for many years and transient visual scotoma diagnosed by the optician as ophthalmic migraine. She was Tinnel's sign negative with no evidence of macroglossia but a chest x-ray done five years previously had shown cardiomegaly. She had also undergone a colonoscopy a few years previously that revealed polyps which were biopsied and removed. Subsequent investigation showed a raised random GH of 3.9 and IGF of 142.9 an OGTT failed to suppress her GH. An MRI was arranged which demonstrated a pituitary microadenoma and after discussion of her diagnosis she was started on Cabergoline 0.5mg.
The patient underwent visual field testing which showed no bitemporal hemianopia but some changes consistent with glaucoma. An echocardiogram showed only very mild aortic regurgitation. She was subsequently discussed at a Pituitary MDT meeting in June 2008 which favored continuation of her medical management with continued cabergoline three times a week, to which she had made a good response with IGF just 32 (normal 6-30), rather than any surgical intervention. She undergoes regular IGF monitoring but no further dynamic testing. An attempt to stop her Carbimazole in January 2009 was unsuccessful and it was restarted in May 2009. She was referred to Nuclear Medicine and underwent Radioiodine therapy (820MBq) in June 2009 and thereafter remained chemically and clinically euthyroid. She will undergo regular screening colonoscopies given the previous polyps (albeit benign) and the significantly increased mortality rate of colorectal cancer in acromegaly patients (x 2.4). (2)
This case demonstrates the importance of global assessment of patients referred for specialist review as the presenting issue transpired not to be the principal one. The case also reflects the value of multidisciplinary input with endocrine, radiological and neurosurgical opinions playing a pivotal role in diagnosis and management. Cabergoline is a more effective dopamine agonist, though not often used first-line, as in this case, (in favor of somatostatin analogues such as octreotide), which achieves an effective response in approximately 45% of patients.(1)
1: Melmed S, Ho K, Klibanski A, et al. Clinical review 75: Recent advances in pathogenesis, diagnosis, and management of acromegaly. J Clin Endocrinol Metab. Dec 1995;80(12):3395-402
2: Orme SM, McNally RJQ, Cartwright RA, Belchetz PE. Mortality and cancer incidence in acromegaly: A retrospective cohort study. J Clin Endocrinol Metab. 1998;83:2730-2734.