Pituitary enlargement on magnetic resonance imaging in congenital hypothyroidism

Objective: To assess pretreatment and posttreatment pituitary gland size by magnetic resonance imaging in children with subtle or overt signs of long-standing hypothyroidism. Design: Etiologic diagnosis of hypothyroidism was confirmed by thyrotropin, triiodothyronine, and thyroxine assays; thyroid antibody tests; and radionuclide thyroid scan. Repeated magnetic resonance imaging was obtained after 6 to 12 months of therapy with levothyroxine sodium to restore a euthyroid state. Setting: Endocrine service at a hospital for children in Bombay, India. Patients: Ten children whose mean (+/-SD) chronologic age, bone age, and duration of symptoms were 11.39+/-1.81, 3.78+/-2.05, and 6.95+/-2.91 years, respectively. One patient was seen for acute neurologic symptoms suggesting a suprasellar lesion. Results: Magnetic resonance imaging showed homogeneous diffuse enlargement of the pituitary gland in all patients. The superior margin of the gland was flat in five patients and convex in the rest, with suprasellar extension and partial or complete obliteration of the infundibulum in three and mild compression of optic chiasma in two, thus mimicking a sellar or suprasellar tumor. Pretreatment pituitary mean (+/-SD) vertical height in the coronal plane was 10.02+/-2.24 mm, with a posttreatment regression to 4.93+/-1.11 mm (P<.001, Student's t test) and restoration of clinical and hormonal euthyroid status. Conclusion: Awareness of pituitary enlargement and the rare occurrence of neurologic symptoms and chiasmal syndrome are important in children with longstanding congenital hypothyroidism.