A 46 year old woman who lives in UK complains of weight gain, constipation and sensitivity to cold

A 46 year old woman who lives in UK complains of weight gain, constipation and
sensitivity to cold. Her pulse is regular at 50 beats/minute. What is the SINGLE most
likely underlying mechanism for her condition?

A. Autoimmune
B. Degenerative
C. Congenital
D. Infective
E. Nutritional