Isolated Central Hypothyroidism in an Adolescent With Narcolepsy.

Isolated central hypothyroidism (ICH) and narcolepsy are conditions rarely seen in the pediatric population which are usually characterized by delayed diagnosis and treatment due to their variable presentation and subclinical onset. We describe an unusual case of an adolescent male diagnosed with narcolepsy and central hypothyroidism. A 15-year-old obese boy presented with the complaint of excessive daytime sleepiness, fatigue, and snoring. Obstructive sleep apnea (OSA) was initially suspected as the underlying cause, but the sleep study was negative for OSA. However, the multiple sleep latency test was consistent with narcolepsy without cataplexy. He was then started on modafinil, but his symptoms persisted. Thyroid function tests were performed that were consistent with ICH. Thyroid replacement therapy was initiated with subsequent improvement in symptoms. A theoretical association exists between narcolepsy and ICH due to the involvement of the hypothalamus and pituitary gland. Nevertheless, clinical association, as seen in our case, is rare. Central hypothyroidism is a known etiology leading to fatigue and sleepiness. Narcolepsy without cataplexy can have overlapping symptoms with hypothyroidism, as seen in our patient. The presence of narcolepsy should prompt screening for hypothyroidism in appropriate clinical settings.