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The endocrine system is the body's network of hormone-producing glands that regulates metabolism, growth, mood, reproduction, and blood sugar through chemical messengers carried in the blood.
Reviewed & updated
The endocrine system is the body's network of glands that produce and release hormones—chemical messengers that travel through the bloodstream to control how organs and tissues work. Unlike the nervous system, which sends fast electrical signals, the endocrine system works more slowly and broadly, regulating processes that unfold over minutes, hours, days, or years.
Hormones direct nearly every essential function, including metabolism, growth and development, mood and sleep, reproduction, blood sugar control, blood pressure, and the body's response to stress. Because a single hormone can affect many organs at once, even small imbalances can have widespread effects.
Endocrine glands are ductless—they release hormones directly into the blood rather than through tubes. Each hormone binds to specific receptors on target cells, like a key fitting a lock, triggering a precise response.
The endocrine system is coordinated by the hypothalamus in the brain, which links the endocrine and nervous systems. The hypothalamus signals the pituitary gland, often called the "master gland," which in turn directs many other glands.
Most hormones are kept in balance by negative feedback loops. When a hormone rises to the right level, it signals the brain to slow further production—much like a thermostat shutting off once a room reaches the set temperature. For example, rising thyroid hormone tells the pituitary to reduce thyroid-stimulating hormone (TSH), and rising cortisol suppresses the signals that triggered its release.
Endocrine disorders generally involve too much hormone, too little hormone, or how the body responds to it. The conditions below are common examples and are described for general education only.
These conditions are diagnosed by a qualified clinician using blood tests that measure hormone levels, often alongside imaging. This information is not a tool for self-diagnosis.
No supplement or routine can guarantee hormonal balance, but these evidence-based habits support healthy function for most people:
> When to see a doctor: Persistent fatigue, unexplained weight changes, excessive thirst or urination, mood changes, or irregular periods can signal a hormonal issue. An endocrinologist specializes in diagnosing and treating these conditions.
*This article is for educational purposes and is not a substitute for professional medical advice. Consult a qualified healthcare provider for diagnosis and treatment.*
In-depth, independently reviewed guides to the major organs and structures of this system.
This guide draws on 14 peer-reviewed and authoritative sources (StatPearls, NIH/NHLBI, MedlinePlus, and primary literature).