Scenario 4: Hypothyroidism

A patient  walked into your  clinic today with the following complaints: Weight gain (15 pounds), however has a decreased appetite with extreme fatigue,  cold intolerance, dry skin, hair loss, and falls asleep watching television. The patient also tearfulness with depression, and with an unknown cause and has noted she is more forgetful.  She does have blurry vision.

PMH: Non-contributory.

Vitals: Temp 96.4˚F, pulse 58 and regular, BP 106/92,  12 respirations. Dull facial expression with coarse facial features. Periorbital puffiness noted.

Diagnosis: hypothyroidism.

Question:

What causes hypothyroidism?