**3.2 Dietary factors**

## *3.2.1 Iodine deficiency*

Twenty-nine percent of world population lives in area where soil is deficient in iodine, e.g., the Himalayan region in India. The most common cause of goiter worldwide is iodine deficiency. More than 30% of population having median urine iodine less than 20 mcg/l developed goiter [9]. Daily requirement of iodine is 100–150 mcg/day, but the requirement increases in pregnant and lactating women.

#### *3.2.2 Dietary goitrogens*

Soy and Millet contains flavonoids which impair thyroid peroxidase activity. Cyanogenic glucosides in Cassava, Lima beans compete for iodine uptake in thyroid follicles. Similarly cruciferous vegetables like cabbage cauliflower, broccoli contains glucosinolates which also competes with thyroidal iodine uptake.

#### **3.3 Drugs causing goiter**

Drugs like Lithium, Amiodarone apart from Antithyroid drugs are known to cause goiter. Rare causes include Interferon Alfa, Rifampicin, Phenytoin, and Phenobarbitone.

#### **3.4 Hashimotos thyroiditis**

The condition is named after Japanese physician Hakaru Hashimoto. This autoimmune thyroid disorder is characterized by diffuse lymphocytic infiltration of thyroid gland along with follicular destruction. Serologically the patients have high titer of anti-thyroglobulin and anti TPO antibodies. Hashimoto's thyroiditis is the next most common cause of hypothyroidism after iodine deficiency. But subset of patient may remain clinically and biochemically euthyroid for rest of the life. The condition has female to male prevalence ratio of 7:1.
