Mammals secrete hormones via their endocrine glands to control many functions in the body including the stress response, digestion, reproduction, etc. Hormones are chemicals which bind to specific receptors on cells if present, and initiate a response. This is either directly by entering cells and binding transcription factors, or indirectly via a second messenger which then cascades the signal down and activates enzymes.

You love cats, don’t lie. The pituitary gland secretes many different hormones as the master gland, with the ability to control other glands. These include growth hormones, thyroid stimulating hormones and hormones involved in reproduction and lactation. The thyroid gland secretes hormones involved in metabolism and protein synthesis, while the nearby parathyroid glands secrete hormones that control blood and bone calcium content.

The adrenal glands secrete hormones such as adrenaline and cortisol, involved in metabolism and immune function, while the pancreas secretes insulin and glucagon to maintain a steady blood glucose concentration. Finally, the ovaries and testes secrete hormones such as oestrogen, progesterone and testosterone at the direction of hormones produced by the pituitary. These act on the production of gametes, secondary sexual characteristics and…