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• Hormone produce their effects on target tissues by binding to specific protein
called hormone receptors located in the target tissue.

• Binding of hormones to receptor leads to the formation of hormone receptor
complex. This binding leads to change in target tissue.

On the basis of chemical nature, hormones are
grouped as-

1. Peptide, polypeptide and protein hormones- insulin, glucagon, pituitary

hormone, hypothalamic hormones.

2. Steroids- cortisol, testosterone, progesterone.
3. Idothyronines- thyroid hormones.

4. Amino acid derivatives- epinephrine.

The hormones that bind with membrane bound receptors normally do not enter the
target cells but generate second messenger which in turn regulate cellular metabolism.

The hormones (steroid hormones) which interact with intracellular receptors mostly
regulate gene expression or chromosome function by interaction with hormone-

receptor complex with the genome. These biochemical actions results in physiological
and developmental effects

.