Hormones: Key Concepts 😊

What Are Hormones?

Hormones are molecules that act as intercellular messengers. They’re made by endocrine glands and released directly into the bloodstream, which carries them to their target organs :contentReference[oaicite:0]{index=0}.

Chemical Nature of Hormones

  • Steroids (e.g., estrogens, androgens)
  • Polypeptides (e.g., insulin, endorphins)
  • Amino‐acid derivatives (e.g., epinephrine, norepinephrine) :contentReference[oaicite:1]{index=1}

Main Functions of Hormones

  • Keep biological activities in balance 🎯
  • Regulate blood glucose:
    • Insulin lowers blood glucose when it rises sharply
    • Glucagon raises blood glucose when it falls too low
    Together, they maintain a steady glucose level in blood :contentReference[oaicite:2]{index=2}.
  • Epinephrine & Norepinephrine trigger “fight-or-flight” responses to external stimuli ⚡️ :contentReference[oaicite:3]{index=3}
  • Growth hormone & Sex hormones support growth, development, and reproduction 🌱
  • Thyroxine (an iodinated tyrosine derivative) regulates metabolism:
    • Low thyroxine → hypothyroidism (lethargy, weight gain)
    • High thyroxine → hyperthyroidism (restlessness, weight loss)
    • Iodine deficiency → enlarged thyroid (goiter); prevented by iodised salt 🧂
    :contentReference[oaicite:4]{index=4}

Steroid Hormones from Adrenal Cortex & Gonads

  • Glucocorticoids: control carbohydrate metabolism, modulate inflammation, aid stress response
  • Mineralocorticoids: regulate water & salt excretion by kidneys
  • Addison’s disease arises when adrenal cortex fails—symptoms include low blood sugar, weakness, stress intolerance; treated with glucocorticoid & mineralocorticoid therapy
  • Testosterone: drives male secondary traits (deep voice, facial hair) 🧔
  • Estradiol: drives female secondary traits, controls menstrual cycle
  • Progesterone: prepares uterus for implantation 🤰 :contentReference[oaicite:5]{index=5}

Important Concepts for NEET

  • Classification by chemical nature (steroids, peptides, amino‐acid derivatives)
  • Hormonal regulation of blood glucose: insulin vs glucagon
  • Role of thyroid hormone (thyroxine) and dietary iodine
  • Functions of adrenal cortex hormones & Addison’s disease
  • Gonadal hormones & development of secondary sexual characteristics