Fact 1: Thyroid hormones increase the rate of metabolism in cells throughout the body.

Fact 2: Thyroid hormone is made by the thyroid gland.

Given the two facts above, answer the question "What increases metabolism in cells throughout the body?" with the following options: 
- lymph nodes
 - aerobic capacity
 - puberty
 - thyroid gland
 - Smoking
 - smoking cigarettes
 - cells
 - heat energy


 

    thyroid gland     