Hormones: what they are, types, and what they do

Hormones are chemical messengers that are carried by the blood to tissues and organs and affect growth, metabolism, sexual function, reproduction, and mood. They act slowly, but even a very small amount can noticeably change how cells work. Below is a reference map: what these substances are, which glands produce them, what sex hormones do, and when a doctor orders testing.

What hormones are and how they act

Hormones are biologically active substances produced in specialized cells of the endocrine glands; they enter the blood, bind to receptors on target cells, and regulate metabolism and physiological functions. Receptors are located differently: steroid hormones have receptors in the cell nucleus, while protein and peptide hormones have receptors on the outer surface of the membrane. Hormones act at extremely low concentrations, so an excess or deficiency of a single substance affects the entire body.

Key point: hormones act at extremely low concentrations — even a small amount of a hormone noticeably changes how cells work.

Which glands produce hormones

The main endocrine glands are the pituitary gland, pineal gland, thymus, thyroid gland, adrenal glands, and pancreas. In addition, men produce hormones in the testes and women in the ovaries. The system is hierarchical: the hypothalamus produces releasing factors and sends them to the pituitary not through the general bloodstream but through the portal vascular system; under their action, the production of pituitary tropic hormones speeds up or slows down. Tropic hormones reach a specific gland and influence the synthesis of its hormone, and both direct and feedback relationships operate between the gland and the hormone.

Key point: the glands work as a network, not individually.

Main hormones and what they do

Science knows more than 100 substances characterized by hormonal activity. Their effects can be conveniently grouped.

• growth, development, and maturation of the body, including preparation for puberty;
• metabolism — how the body obtains energy from food;
• sexual function, the reproductive cycle, sexual desire, preparation for childbirth and menopause;
• mood, the immune system, hunger and satiety;
• production and secretion of other hormones.

Hormones interact: synergism is unidirectional action (glucagon and adrenaline raise glucose levels), antagonism is opposite action (glucagon and insulin).

Key point: there are direct and feedback relationships between hormones and glands — they are united into a single system.

Sex hormones in women and men

Sex hormones in women are produced in the ovaries and in men in the testes. They participate in sexual function and reproduction, control the reproductive cycle, influence sexual desire, and prepare the body for the next life stage — puberty, childbirth, and menopause. Sex hormone testing consists of laboratory tests that measure the level of a substance in blood, urine, or saliva; the list includes tests for estrogens, progesterone, testosterone, prolactin, anti-Müllerian hormone, and SHBG.

What hormonal disorders are

A hormonal disorder is a situation in which too much or too little of a hormone is produced. Hormones are potent, so an excess or deficiency of even one of them can be serious. Insufficient or excessive synthesis affects the molecular mechanisms regulating metabolism and contributes to the development of diseases of the endocrine glands. Endocrine disorders include obesity, diabetes, osteoporosis, hormone-dependent cancers, and hormonal imbalances.

Key point: an excess or deficiency of a hormone can be serious.

When hormone testing is ordered and when to see a doctor

Testing is ordered by a doctor when there are symptoms of a hormonal disorder, and the results are assessed by an endocrinologist during an appointment.

Key point: a test is evidence, not a diagnosis; the decision is made by a doctor.

Hormonal disorders on their own are not a reason to call an ambulance; 103/112 — for life-threatening conditions, for example signs of stroke or heart attack.

This material is for reference and does not replace a doctor's consultation: only a doctor during an appointment can correlate symptoms, examination, and test results.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer