BharatNotes What is Hormones (Endocrine)?
Hormones are chemical messengers produced by endocrine glands — ductless glands that secrete directly into the bloodstream rather than through a duct. Carried by blood, a hormone acts only on target cells bearing the matching receptor, regulating slow, sustained processes such as metabolism, growth, reproduction, water balance and the stress response. This contrasts with exocrine glands (salivary, sweat, digestive), which release secretions through ducts onto a surface or into a cavity.
Major Glands and Their Hormones
The principal endocrine glands include the hypothalamus, pituitary, pineal, thyroid, parathyroid, adrenals, pancreas and the gonads (ovaries/testes).
| Gland | Key hormone(s) | Main function |
|---|---|---|
| Pituitary ("master gland") | Growth hormone, TSH, ACTH, FSH, LH, prolactin | Controls other glands; growth |
| Thyroid | Thyroxine (T4), Triiodothyronine (T3) | Raises metabolic rate (needs iodine) |
| Parathyroid | Parathyroid hormone | Regulates blood calcium |
| Adrenal | Adrenaline, cortisol | "Fight-or-flight", stress, BP |
| Pancreas (islets of Langerhans) | Insulin (beta cells), glucagon (alpha cells) | Lower / raise blood glucose |
| Pineal | Melatonin | Sleep-wake (circadian) cycle |
Key Features
- Chemical classes: hormones are broadly amino-acid-derived (peptides, proteins, amines such as adrenaline and thyroxine) or steroid hormones derived from cholesterol (e.g., cortisol, sex hormones).
- Master control: the pituitary, at the base of the brain, directs many other glands under instructions from the hypothalamus, linking the nervous and endocrine systems.
- Feedback loops: secretion is self-regulating — rising blood glucose triggers insulin; falling glucose triggers glucagon, the two acting in opposition to maintain homeostasis.
Significance and Current Status (India)
Endocrine disorders are a growing public-health challenge. Iodine is essential for thyroid hormones; its deficiency causes goitre, cretinism and stillbirths. The Government launched the National Goitre Control Programme in 1962, renamed the National Iodine Deficiency Disorders Control Programme (NIDDCP) in August 1992 (Directorate General of Health Services). Universal salt iodisation remains the core strategy.
The ICMR-INDIAB study (Phase covering 31 states/UTs, published in The Lancet Diabetes & Endocrinology, 2023) estimated a national diabetes prevalence of 11.4% and prediabetes of 15.3% among adults — reflecting the failure of insulin regulation and India's rising non-communicable disease burden.
UPSC Angle
Prelims favours precise gland-hormone-function matching and deficiency diseases (iodine-thyroxine-goitre; insulin-pancreas-diabetes). Mains GS2/GS3 links the topic to public health, nutrition and NCDs — the NIDDCP, salt iodisation, and the diabetes epidemic flagged by ICMR-INDIAB. As a base biology concept it underpins recurring questions on the human body, lifestyle diseases and India's health policy. Foundation concept — no direct PYQ; supports the human-physiology and public-health question family.
