MON-058 Precocious Puberty and Hypothyroidism in a Pediatric Case

Background: Hypothyroidism with secondary sellar/suprasellar mass is rarely associated with precocious puberty. Here we describe a rare case of pediatric hyperprolactinemia and precocious puberty secondary to hypothyroidism, marked TSH elevation, and pituitary hyperplasia. Clinical Case: A 9-year-old female, with onset of thelarche and menses occurring at age 7 and 8 respectively, presented with primary hypothyroidism (Free T4 <0.11; n=4.9-11.4mcg/mL), elevated TSH (1620.0mU/mL; n=0.3-4.7mU/mL), hyperprolactinemia (108.6ng/mL; n=3.0-23.1ng/mL), and elevated serum estradiol (37.6pg/mL; n=10pg/mL). The patient had coarse scaly skin, diminished energy, and poor growth lasting 1 year. There were no associated gastrointestinal issues, temperature intolerance, nor visual impairments noted during this time. Magnetic resonance imaging revealed a large mass (1.48cm) with suprasellar extension and a mass effect on the optic chiasm. The patient was then started on Levothyroxine and Cabergoline, to reduce serum prolactin levels. However, upon follow-up two months later, the patient had hypoprolactinemia (2.0ng/mL; n=3.0-23.1ng/mL). The patient was referred to neurosurgery for resection of the sellar mass. Endocrinology was also consulted, at which point Cabergoline was discontinued and Levothyroxine was gradually increased. Follow up 4 months later showed prolactin levels had normalized to 11.4ng/mL (3.0-23.1ng/mL). Serum LH and FSH were within normal ranges (1.2mIU/mL and 4.2mIU/mL, respectively). TSH, though still elevated (47.35mU/mL; n=0.3-4.7mU/mL), was significantly reduced compared to the prior measurement (1620mU/mL). Serum levels of Free T4 increased to 1.06mcg/mL (n=4.9-11.4mcg/mL). Levothyroxine was titrated up and a repeated pituitary MRI demonstrated a significant decrease in the size of the mass with resolution of the suprasellar extension and mass effect on the optic chiasm. Further, the patient’s menses ceased and thelarche resolved upon correction of T4 and regression of the pituitary mass. Conclusions: While rare, primary hypothyroidism and TSH-driven pituitary hyperplasia can result in a large mass effect with suprasellar extension, causing secondary hyperprolactinemia by a mass effect and central precocious puberty. This case highlights the benefits for evaluating underlying hypothyroidism as a cause for hyperprolactinemia and sellar/suprasellar mass.