These are chemical messengers produced by endocrine glands that travel through the bloodstream to target cells and organs, influencing a wide range of processes. 

This system includes glands like the pituitary, thyroid, adrenal, pancreas, ovaries, and testes, which secrete hormones. 

Endocrinologists address conditions like diabetes, thyroid disorders, osteoporosis, and issues related to sex hormones. 

These can arise from either overproduction or underproduction of hormones, leading to various health problems.