Endocrine Abstracts

Acromegaly and thyroid-associated ophthalmopathy(TAO) are uncommon diseases with different pathogenetic mechanisms.We report two patients with acromegaly and TAO and speculate on a possible association.

A 54 year old man with subclinical hypothyroidism and strongly positive thyroid microsomal antibodies presented with features of TAO.MRI of his orbits confirmed the diagnosis.Clinical examination also revealed features suggestive of acromegaly,which was confirmed biochemically.MRI of his pituitary revealed a pituitary microadenoma.

A 53 year old lady presented with irritable watery eyes.She was clinically and biochemically euthyroid but had strong family history of autoimmune disease.Clinically she had mild TAO.Orbital MRI showed enlarged extraocular muscles consistent with TAO.A pituitary macroadenoma was also evident and further clinical examination showed features of acromegaly,which was confirmed biochemically.Six months later she developed thyrotoxicosis due to Grave's disease.

Extraocular muscle enlargement is the hallmark of TAO.Inflammatory cytokines generated as a result of an autoimmune process against orbital antigens are thought to drive this phenomenon.Increased IGF-1 immunoreactivity in the orbit and antibodies that promote growth of extraocular muscle as well as antibodies that bind to orbital IGF-1 receptor have been described in TAO.We propose that elevated serum IGF-1 as occurs in acromegaly may render acromegalic patients who are predisposed to orbital autoimmunity more likely to manifest clinical features of TAO.