THYROID HEMIAGENESIS ASSOCIATED WITH POSSIBLE HASHIMOTO’S THYROIDITIS IN THE REMAINING LOBE PRESENTING AS LATE-ONSET HYPOTHYROIDISM IN ADULTHOOD

Abstract

BACKGROUND
Thyroid hemiagenesis is a very rare abnormality, usually discovered incidentally during the evaluation of unrelated thyroid disorders. In thyroid hemiagenesis, the left lobe tends to be absent with concomitant compensatory enlargement of the opposite lobe. Thyroid hemiagenesis per se is typically not associated with hypothyroidism. Here, we present an unusual case of thyroid hemiagenesis associated with possible Hashimoto’s thyroiditis.

CASE
A 36-year-old Thai female with no known underlying disease presented with fatigue, chills, and weight gain for 6 months. She was given levothyroxine 75 μg/day based on results of her thyroid function tests at the previous hospital. However, her symptoms persisted. She denied family history of thyroid disorders and had no history of neck radiation. Initial blood tests at our hospital showed subclinical hypothyroidism (slightly elevated TSH level at 4.86 mIU/L; reference range 0.27-4.20 mIU/L) with negative thyroid auto-antibodies. Physical examination showed nonpalpable thyroid gland. Her thyroid ultrasound revealed absent left thyroid lobe and atrophic right thyroid lobe with heterogeneous echotexture, compatible with possible Hashimoto’s thyroiditis. FNA was no longer done to confirm the Hashimoto’s thyroiditis. Levothyroxine was increased to 100 μg/day to keep her TSH level in the mid-normal range. During a 3-year follow- up period, the patient remains in a stable condition.

CONCLUSION
Thyroid ultrasonography should be performed in all patients with spontaneous hypothyroidism. Individuals with thyroid hemiagenesis are prone to develop additional thyroid pathologies. Close monitoring is required to detect concomitant disorders.