Endocrine Abstracts

Introduction: The commonest cause of orbitopathy is Graves’ disease but the differential diagnosis includes primary and secondary neoplasia, inflammatory, vascular and infective causes. We report an exceedingly rare case of orbitopathy as the presenting feature of Acromegaly.

Case report: A 43 year old lady presented with ‘periorbital puffiness’ and irritable eyes. Clinical evaluation revealed orbitopathy and magnetic resonance imaging (MRI) demonstrated enlarged extraocular muscles but no other pathology. She was clinically and biochemically euthyroid with a negative thyroid autoantibody screen. She re-presented 3 years later with sweating and clinically apparent soft tissue features of Acromegaly. The biochemical diagnosis of Acromegaly was confirmed and MRI demonstrated a pituitary macroadeoma extending into the suprasellar cistern but with no chiasmal compression or cavernous sinus extension. Following pituitary adenomectomy the patient reported an improved orbital appearance.

Discussion: There have been very rare case reports where orbitopathy was documented as being the presenting feature of Acromegaly. One case report describes bilateral eyelid swelling in association with enlarged extraocular muscles preceding the diagnosis of Acromegaly by six years.

It is slightly more apparent that orbitopathy is documented in established Acromegaly. In one retrospective review of 137 orbital scans demonstrating extraocular muscle enlargement Graves’ accounted for 49% of the cases and Acromegaly 2% (3 cases). There are no pathognomonic radiological features of the extraocular muscles in Acromegaly which typically causes diffuse, bilateral enlargement similar to Graves’ disease.

It is interesting to note that extraocular muscle enlargement is the hallmark of thyroid associated orbitopathy (TAO) and that increased levels of IGF-1 have been demonstrated in the extraocular muscle of patients with TAO. In vitro studies have established the ability of IGF-1 to stimulate the excessive production of glycosaminoglycans and collagen by orbital fibroblasts. Acromegaly may mediate increased IGF-1 immunoreactivity in the orbit resulting in an orbitopathy indistinguishable from TAO.