mechanism of hormone action

• protein hormones interact with membrane-bound receptors
• protein hormones generate second messengers such as cyclic AMP, IP3 and calcium ions, which then regulate cellular metabolism
• steroid hormones and iodothyronines bind with intracellular receptors, usually present in the nucleus
• steroid hormones and iodothyronines mostly regulate gene expression or chromosome function by the interaction of hormone-receptor complex with the genome
• hormones secreted by gonads are steroid based
• thyroid hormones are synthesized from tyrosine amino acid
• hormones secreted by the adrenal cortex are steroid based
• hormones secreted by the pituitary gland, hypothalamus and pancreas are peptide based
• hormones secreted by the adrenal medulla are amino acid derivatives