The curious case of vanishing hypothyroidism

ABSTRACT Consumptive hypothyroidism (CH) is a severe form of hypothyroidism that occurs due to the expression of high levels of type 3 deiodinase (D3) in tumors. Cavernous hemangiomas (CvH) and arteriovenous malformation (AVM) express high levels of D3. In CvH and AVM, tumoral D3 can cause a unique form of hypothyroidism with degradation in thyroid hormone at rates that exceed the synthetic capacity of the thyroid gland. We present a 36-year-old lady, a diagnosed case of hypothyroidism on levothyroxine 100 mcg, for the preceding 6 years, who was diagnosed with AVM in her right proximal thigh at the current presentation. Following surgery, there was a reduction in the requirement for levothyroxine with subsequent discontinuation. Recognition of CH is imperative as the patients can be taken off levothyroxine after definitive treatment of the primary etiology.