Ans.Pituitary Gland
It is a pea-shaped gland attached to the hypothalamus part of brain. Many hormones (tropic hormones) of pituitary gland influence the secretions of other endocrine glands. However some hormones of this gland act directly on various tissues of body.
Lobes of Pituitary Gland
There are two lobes of pituitary gland i.e. anterior lobe and posterior lobe.
1.Anterior Lobe
It produces many hormones.
i) One of its important hormones is somatotrophin (growth hormone). It promotes the growth of body. If the production of this hormone is diminished during growing age, the rate of growth decreases. This condition is called dwarfism. If this hormone is excessively produced during growing age, it leads to gigantism (very tall and overweight). If somatotrophin is excessively produced after growing age, internal organs and body extremities alone grow large. This condition is known as acromegaly. Such persons will have large hands, feet and jawbones.
ii)Another important hormone secreted by the anterior lobe of pituitary gland is thyroid-stimulating-hormone (TSH). It stimulates thyroid gland to secrete its hormones. The remaining hormones of anterior lobe influence reproductive organs and also control adrenal glands.
2.Posterior Lobe ,
The posterior lobe of pituitary gland stores and secretes two hormones i.e. oxytocin aad vasopressin (anti diuretic hormone, ADH). These hormones are produced by hypothalamus (a part of brain).
i)Vasopressin increases the rate of reabsorption of water from nephrons. When we have low amount of water in body fluids, pituitary gland secretes vasopressin and so more reabsorption of water occurs from nephrons into blood. In this way, body retains water and less amount of urine is produced. On the other hand, when body fluids have more than normal water, there is a decline in the secretion of this hormone. If pituitary gland does -not secrete this hormone in the required amount, less water is reabsorbed from nephrons and there is excessive loss of water through urine. This condition is known as diabetes insipidus.
ii) The hormone, oxytocin stimulates the contraction of uterus walls in mothers for child birth. Moreover, this hormone is necessary for the ejection of milk from breast.