The basal metabolic rate in the body is regulated by a negative feedback loop involving the thyroid gland.
The diagram shows how this pathway takes place.

Which numbers on the diagram represent the hormones TSH (Thyroid-Stimulating Hormone) and thyroxine?
1=TSH1 = \text{TSH}1=TSH and 3=thyroxine3 = \text{thyroxine}3=thyroxine
2=TSH2 = \text{TSH}2=TSH and 3=thyroxine3 = \text{thyroxine}3=thyroxine
2=thyroxine2 = \text{thyroxine}2=thyroxine and 3=TSH3 = \text{TSH}3=TSH
3=TSH3 = \text{TSH}3=TSH and 4=thyroxine4 = \text{thyroxine}4=thyroxine