What are hormones? Give their classification. State the biological importance of hormones.

(N/A) Hormones are molecules that act as intercellular messengers. They are secreted by endocrine glands in the body,poured directly into the bloodstream,and transported to the site of action.
Classification: Chemically,hormones are classified as steroid hormones,peptide hormones,and amine hormones.
$i$. Peptide hormones: Examples include insulin and endorphins. Insulin maintains blood sugar levels by responding to glucose spikes,while glucagon increases blood glucose levels. Together,they regulate glucose homeostasis.
$ii$. Amine hormones: Examples include epinephrine and norepinephrine,which mediate responses to external stimuli. Thyroxine,an iodinated derivative of the amino acid tyrosine,regulates metabolism. Low levels cause hypothyroidism (lethargy,obesity),while high levels cause hyperthyroidism. Iodine deficiency leads to goiter,which is managed by iodized salt.
$iii$. Steroid hormones: Produced by the adrenal cortex and gonads. Glucocorticoids control carbohydrate metabolism and stress responses. Mineralocorticoids regulate water and salt excretion by the kidneys. Dysfunction of the adrenal cortex can lead to Addison's disease. Gonadal hormones like testosterone (male) and estradiol/progesterone (female) are responsible for secondary sexual characteristics and reproductive functions.