The four endocrine glands are:
1. Pineal gland,
2. Thymus gland,
3. Parathyroid gland,
4. Adrenal gland.
1. Pineal gland: This gland is situated on the mid-dorsal surface of posterior part of the anterior brain. It is poly-lobed. It is somewhat flattened and round structure. It secretes melatonin hormone which inhibit ovarian growth and ovulation. It controls and regulates menstrual cycle, activity and development of gonads.
2. Thymus gland: Thymus gland is located just above the heart and under the chest bone. It develops from birth to youth and afterwards, its size begins to decrease.
The gland secretes thymosin. Thymosin I and Thymosin II. It produces lymphocytes. These hormones inspire lymphocytes to destroy germs and antigens. Thus, these hormones are helpful in the security system of the body.
3. Parathyroid glands: These glands are embedded in thyroid gland on its dorsal surface. It is two pairs,
4. Adrenal gland: Its hormone is called parathormone. This hormone controls the number of calcium and phosphate ions. It also controls the development of bones and formation of teeth. Deficiency of parathormone hormone causes contraction of muscles, for a long time. This disease is called tetany.
Oversecretion of parathormone rot the bones, so the bones become slender, weak and brittle. This condition is called osteoporosis.
Adrenal gland: Adrenal gland is present on the upper end of each kidney, fitting like a cap. It is also called supra-renal gland. The gland consists of two regions-the outer is called cortex and the inner one is called medulla.
Cortex:
The cortex secretes three hormones (C-orticoids).
1. Mineralocorticoid,
2. Glucocorticoid
3. Gonadocorticoid
1. Mineralocorticoid: This hormone regulates the balance between sodium and potassium ions in the blood. If this hormone becomes deficient, more sodium is excreted through the urine and cardiac output is reduced. This can even cause death. This hormone is thus, known as “the life-saving hormone”.
2. Glucocorticoid: This is concerned with carbohydrate metabolism and hence, called glucocorticoid. This hormone creates the ability in the body to resist diseases. This hormone controls energy formation and protein synthesis, in the body.
3. Gonadocorticoid: The cortex of the adrenal gland secretes the male hormone, androgen and also a female hormone. Both are called gonadocorticoid hormones. Any imbalance in the amounts of these hormones, might lead to a change of sex also. In women, if more androgen is secreted, male characteristics start appearing i.e. moustaches appear.
