Hormone
Definition
A hormone is a chemical messenger produced by endocrine glands and transported through the bloodstream to target organs where it regulates physiological processes. Hormones can be proteins, steroids, or amino acid derivatives. They are essential for growth, metabolism, reproduction, and homeostasis.
Key Points for NEET
- 1Secreted by endocrine glands (ductless glands)
- 2Act on specific target cells with receptors
- 3Three types: peptide, steroid, and amine hormones
- 4Regulated by feedback mechanisms
- 5Examples: insulin, thyroxine, testosterone, estrogen
Example
Insulin released by pancreas to lower blood glucose after a meal
Asked in NEET
Common Mistakes to Avoid
- ✗Confusing endocrine (ductless, blood transport) with exocrine (ducted, local secretion) glands
- ✗Thinking all hormones are proteins — steroids (testosterone, estrogen) are lipid-derived, not proteins
- ✗Mixing up the source glands: e.g., insulin from pancreas (not liver), thyroxine from thyroid (not parathyroid)
Quick Revision Notes
- ⚡Peptide hormones: bind surface receptors (second messenger like cAMP); Steroid hormones: enter cell, bind nuclear receptors
- ⚡Key glands: Pituitary (master gland), Thyroid (T3/T4), Adrenal (cortisol/adrenaline), Pancreas (insulin/glucagon)
- ⚡Hypothalamus controls pituitary via releasing/inhibiting hormones — the "master of master gland"
- ⚡Diabetes: Type 1 (no insulin, autoimmune), Type 2 (insulin resistance) — both cause hyperglycemia
Related Terms
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