Hormones are a class of signaling molecules that are produced by the endocrine glands. They regulate various physiological processes in the body, including growth and development, metabolism, reproduction, and mood. In humans, hormones are essential for maintaining homeostasis and coordinating the complex interactions between different organ systems.
The endocrine glands secrete hormones into the bloodstream, where they are transported to target tissues and organs. Hormone levels in the blood are carefully regulated so that they remain within a narrow range. This regulation is achieved through feedback mechanisms that respond to changes in hormone levels.
There are two main types of hormones: steroid hormones and peptide hormones. Steroid hormones are derived from cholesterol and include all of the sex steroids (estrogens, progestogens, and testosterone) as well as adrenal cortical steroids (corticosteroids). Peptide hormones are proteins or polypeptides that have been cleaved from larger precursor molecules. Examples of peptide hormone families include thyroid hormone, growth hormone, insulin-like growth factor (IGF), glucagon-like peptide (GLP), gastrin-releasing peptide (GRP), cholecystokinin (CCK), secretin family members such as vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP).
The binding of a hormone to its receptor initiates a signaling cascade that leads to changes in gene expression and ultimately results in the desired biological response. Receptors for steroid hormones are located on the plasma membrane while receptors for peptide hormones are typically located intracellularly. Hormone action can also be modulated by interactions with other molecules such as enzymes or membrane proteins.
Hormones play a vital role in many aspects of human health and disease. Imbalances in hormone levels can lead to disorders such as diabetes mellitus, obesity, hypothyroidism, Hashimoto’s disease, Grave’s disease, Addison’s disease, Cushing’s syndrome , acromegaly , gigantism , dwarfism , Turner syndrome , premature ovarian failure , polycystic ovary syndrome , cancers of the endocrine glands such as breast cancer , ovarian cancer , testicular cancer , thyroid cancer . It is therefore important to understand how these molecules function in order to develop effective treatments for hormonal disorders