Anastrozole Improves Final Adult Height in Severe Hypothyroidism With Rapid Pubertal Progression

Severe prolonged hypothyroidism due to Hashimoto thyroiditis may lead to rapid pubertal progression and compromised adult height after initiation of levothyroxine (LT4) therapy. There are no reports of aromatase inhibitor use to augment height in these patients. We describe a patient with severe hypothyroidism and growth failure who experienced rapid pubertal and bone age maturation on initiation of LT4 therapy. Anastrozole was added after 2 years to delay epiphyseal fusion. A boy aged 12 years and 1 month presented to the endocrine clinic with short stature and a markedly delayed bone age of 6 years. Brain magnetic resonance imaging showed a 1.5 × 1.0 × 1.2-cm enlarged lobular anterior pituitary. On examination, his height was -3.5 SD score (SDS) and weight was -2.87 SDS. Laboratory studies showed elevated thyrotropin (TSH) 850.6 μIU/mL, low free thyroxine 0.25 ng/dL, and elevated antithyroid antibodies. LT4 was initiated with normalization of TSH after 6 months. After 2 years of treatment he demonstrated catch-up growth with rapid bone age maturation, and his predicted adult height was compromised at 164.6 cm vs a midparental target height of 175.4 cm. Anastrozole 1 mg once daily was initiated. After 1.5 years of anastrozole treatment, the rate of his bone age advancement had slowed and his linear growth remained robust. The patient's near-final height (167 cm) was 2.4 cm taller than his height prediction prior to starting anastrozole. Anastrozole slowed the rate of bone age advancement in a patient with severe hypothyroidism and rapidly progressive puberty during treatment with LT4, leading to improvement in near-final height.