Ans.This is the largest endocrine gland in human body.
Location: It is present in neck region, below larynx.
Hormones: Thyroid produces thyroxin and calcitonin.
Thyroxin: Iodine is required for the production of this hormone.
Goiter
If a person lacks iodine in diet, thyroid gland cannot make this hormone. In this condition, thyroid gland enlarges. This disorder is called goiter.
Effects of Thyroxin: Thyroxin increases the breakdown of food (oxidation) and release of energy in body. It is also responsible for the growth of body. Hypothyroidism is caused by the under-production of thyroxin. It is characterized by low energy production, in body and slowing down of heart-beat. Hyperthyroidism is caused by over production of thyroxin. Its symptoms are increase in energy production, increased heart-beat, frequent sweating and shivering of hands.
Calcitonin
The thyroid gland produces another hormone called calcitonin. It decreases the level of calcium ions in blood and promotes the absorption of calcium from blood into bones.
Calcitonin and parathormone complement each and regulate the level .of calcium ions in the blood.