Reversible growth failure and complete GH deficiency in a 4-year-old girl with very early Hashimoto's thyroiditis and subsequent hyperplasia of pituitary thyrotroph cells.

<bold>Unlabelled: </bold>Hashimoto's thyroiditis is a well-known cause of growth retardation in adolescence. It is less frequently seen in children and rarely seen in infants. A 4-year-old girl was referred to our clinic for a second opinion before starting growth hormone (GH) treatment. Linear growth had markedly declined in the past 2 years, with height -3.4 standard deviations. GH deficiency was complete. She had dry, gray-sallow skin and bloated abdomen, but no goiter. The parents reported fatigue and constipation. Hormonal evaluation revealed TSH 629.5 mIU/ml, free T4 0.08 ng/dl, and prolactin 17.2 ng/ml. Bone age was 2 years. Antibodies to thyroglobulin and thyroid peroxidase were positive, suggesting Hashimoto's thyroiditis. Brain magnetic resonance imaging showed anterior pituitary hyperplasia. After 3 years of L-thyroxine therapy, she was symptomless, her height was -0.6 standard deviations, and the TSH level was normal. Brain magnetic resonance imaging showed regression of the pituitary hyperplasia.<bold>Conclusions: </bold>This report describes a patient with Hashimoto's thyroiditis and pituitary hyperplasia, both quite rare in very young children. Acquired hypothyroidism may appear after neonatal screening and therefore should not be overlooked in investigations of short stature, even when clinical signs of hypothyroidism are absent.<bold>What Is Known: </bold>• Hashimoto's thyroiditis and pituitary hyperplasia are rare in very young children. • Acquired hypothyroidism can appear after negative neonatal screening and should not be overlooked. What is New: • Short children should be evaluated for growth hormone deficiency but only after excluding other causes, particularly hypothyroidism, as we report a child with this disease but no clinical signs of it. [ABSTRACT FROM AUTHOR]