Conversion of Autoimmune Hypothyroidism to Hyperthyroidism in A Child with Down s Syndrome

Objective: To describe a child with Down s syndrome who has been treated initially of hypothyroidism but converted to hyperthyroidism few years later.Case Report: A 5-year old Saudi boy with Down s syndrome presented to the Pediatrics Department of King Fahad Military Hospital in Khamis Mushayt, Kingdom of Saudi Arabia, with chronic constipation, easy fatigability and cold intolerance. Neck examination revealed a non-enlarged thyroid with no palpable nodules. Ultrasonography revealed increased thyroid vascularity. Hypothyroidism was confirmed by thyroid function tests, which showed a high serum thyrotropin (TSH) level (9.63mU/L), a low Free T3 (FT3) of 2.63pmol/Land a low Free Thyroxine (FT4) of 8.2pmol/L. Levothyroxine (50 meg/day orally) was prescribed. The child was scheduled for follow-up every 3 months with monitoring of his TFTs, symptoms and growth and development parameters. The child remained almost euthyroid for 3 years. The requirement for levothyroxine gradually decreased when TSH levels became between l-3mU/L, i.e., within the normal range, then it was finally stopped. However, in 2013, the child started to become irritable and restless. He developed tremor and sleep disorders. His TSH was less than 0.07mU/L, FT3 was high (6.73pmo/L) and his FT4 level became high (25.47pmol/L). Moreover, several autoantigens and antibodies were detected in high levels. Therefore, the diagnosis of Grave s disease was settled and carbimazole tablets were started and the child s condition was followed-up every 3 months till present.Conclusions: Thyroid dysfunctions are common among Down s syndrome cases. The diagnosis of hypothyroidism does not necessarily mean lifelong replacement of thyroid hormone. Conversion of hypothyroidism to hyperthyroidism should be suspected if a patient with hypothyroidism develops persistent symptoms of hyperthyroidism.