Endocrine Abstracts

We present a case of Graves' disease in association with hemiagenesis of the thyroid gland.

A 61 years old Caucasian man presented with light-headedness, proximal muscle ache and tiredness. Past medical history was unremarkable.

Examination revealed a resting tachycardia. There was no goitre, and no evidence of Graves' ophthalmopathy.

Thyroid profile revealed an FT4 of 42 picomoles per litre (11-24) and a TSH of less than 0.01 micro units per millitre (0.35-5.50) confirming thyrotoxicosis. The diagnosis of Graves' disease was supported by a positive thyroid peroxidase antibodies of 267 international units per millilitre (normal range 0-50) and positive TSH receptor antibodies of 2.4 units per litre (normal range 0-1)

Thyroid scintigraphy and uptake (Tc99m) showed increased uptake at 4.2% which is essentially confined to the right lobe and suggestive of a hyperfunctioning adenoma.

Subsequent ultrasound scan of the thyroid showed complete absence of the left lobe and the diagnosis was re-established as Graves' disease of the right lobe.

He was treated with carbimazole and thyroxine

Hemiagenesis of the thyroid gland is a rare anomaly. It results from failure of embryonic development of one thyroid lobe, usually the left.

This case demonstrates that scintigraphy, performed to evaluate biochemical overactivity, can be misleading when hemiagenesis is present. If these results contrast the overall clinical picture then further imaging should be used to avoid unnecessary surgery or radioactive iodine treatment.

Ultrasonography is the best diagnostic tool for detecting thyroid hemiagenesis.