What are hormones?

Hormones are indeed classified as blood-borne chemical messengers. They are secreted directly into the bloodstream by various glands in the endocrine system, such as the pituitary, thyroid, and adrenal glands, among others. Once in circulation, hormones travel to target organs or tissues where they bind to specific receptors and elicit physiological responses. This signaling mechanism is crucial for various bodily functions, including metabolism, growth and development, tissue function, and mood regulation.

In contrast, while proteins produced by the liver might have specific roles, they do not encompass the broader definition and function of hormones. Similarly, although the heart produces certain chemicals, they do not qualify as hormones in the traditional sense. Neurotransmitters, on the other hand, are localized chemical messengers that function within the nervous system, primarily to transmit signals between nerve cells and not broadly throughout the body like hormones do. This distinction is important in understanding the different mechanisms of communication in the body.