Characteristics and functions of hormones

  • Hormones are secretions of the endocrine glands (or tissues) which enter directly into the blood, without passing through ducts.
  • They are secreted in extremely minute quantities. The amount of hormone released is determined by the body’s needs.
  • Chemically, hormones may be polypeptides and proteins, amino acids and their derivatives or steroids (derived from cholesterol).
  • Their action is distant: A hormone secreted in one part of the body produces an effect in another part of the body, i.e. they act on target cells or organs away from their source.
  • Specific action: Organs and tissues respond specifically to the action of hormones. The response, brought about in an organism by a particular hormone, cannot be induced by another hormone. Also, hormones produced in one species usually show similar influence in other species.
  • Hormones help adjust and restore homeostatic balance. For example, excessive blood sugar stimulates the secretion of the hormone insulin in the pancreas. Insulin converts the excess glucose into glycogen. In case of deficient blood glucose, the adrenal gland releases the hormone adrenaline which helps convert the glycogen back into glucose in the muscles. Thus, the blood glucose level is normalized by hormonal action.
  • Help the body cope with emergency demands such as infection, trauma, emotional stress, dehydration, starvation, hemorrhage and temperature extremes.