-The prevalence of hypothyroidism increases with age due to decreased levels of thyroid stimulating hormone secretion and reserve by the pituitary gland.

-Female to male ratio ranges from 2:1 to 8:1 in various epidemiologic surveys which reflects the high prevalence of autoimmune diseases in the female population.

.1:4000 white infants and 1:30,000 black infants are affected.The cause is unexplained

-Hashimoto’s thyroiditis, the most common cause in North America, runs in families (autoimmune disease).

- Associated with other autoimmune diseases e.g, IDDM and pernicious anemia.