Spontaneous remission of pendulum swinging thyroid disease in Down syndrome

Abstract

Summary

Rare patients who have both thyroid-stimulating hormone (TSH) receptor-stimulating and -blocking antibodies can develop ‘pendulum swinging’ thyroid dysfunction. A 9-year-old girl with Down syndrome was treated with carbimazole for Graves’ disease. After 2 years of treatment, she became profoundly biochemically hypothyroid, and this persisted after carbimazole was discontinued. Low-dose L-thyroxine was commenced. This was subsequently also discontinued as biochemical hyperthyroidism developed. TSH receptor antibody bioassay identified both TSH receptor-stimulating and -blocking antibodies. Mild hyperthyroidism persisted and while consultations regarding definitive treatment were ongoing, medication was not recommenced. Thyroid function normalised spontaneously and she has remained euthyroid for the past 3 years. Previous reports have advised definitive treatment; however, our patient developed spontaneous remission which has been prolonged and definitive therapies have been avoided. It is not yet known how commonly this particular phenomenon occurs.

Learning points

• Rare patients who have both TSH receptor-stimulating and -blocking antibodies can switch between hyperthyroidism and hypothyroidism or vice versa during treatment with antithyroid drugs or thyroxine.

• Metamorphic thyroid autoimmunity is more common in Down syndrome.

• Switching between hyperthyroidism and hypothyroidism and back again is less commonly reported.

• Definitive treatment such as radioactive iodine or thyroidectomy are usually recommended.

• Prolonged remission was achieved off all medication, without recourse to definitive treatments.