Primary hypothyroidism, precocious puberty and hypothalamic obesity in Langerhans cell histiocytosis.

A 5 year old girl presented with central diabetes insipidus and primary hypothyroidism. No clinical or radiological evidence of Langerhans cell histiocytosis (LCH) was present. Absent posterior pituitary bright spot was seen in magnetic resonance imaging of the brain. She subsequently developed severe headache, massive obesity, accelerated growth and thelarche. A repeat MRI of the brain revealed hypothalamic tumor. Hormonal investigations revealed, paradoxically, undetectable growth hormone on a clonidine stimulation test. Langerhans cell histiocytosis was proved on electron microscopy of the thyroid tissue. There needs to be a high degree of suspicion for LCH as an etiology of primary hypothyroidism, especially in the presence of diabetes insipidus. Precocious puberty, accelerated growth despite growth hormone deficiency, hypothalamic obesity may occur in pediatric LCH. CNS lesions may have an evolving course, thus repeat neuroimaging is important.