Pituitary gland is a miraculous endocrine gland located in the bone pocket (pituitary fossa) at the base of brain. In human, it is the size of a pea and weighs about 0.5 grams.
Pituitary is one of the most important glands of our body. One can’t live without a normally functioning pituitary. It has very few hormones which act directly, but it functions by regulating the secretions of various glands in our body. So, it is also called Master Gland because it regulates the other glands. It regulates body growth and governs the secretion of many hormones involved maintaining blood pressure and blood glucose levels. It regulates the secretions of thyroid gland, adrenal gland, gonads and breast etc. It also secretes hormones involved in normal menstrual cycle of females. Sex hormones are secreted under influence of the hormones secreted by it. So, normal pituitary is crucial for life.
Pituitary gland is divided into three parts: anterior, intermediate and posterior pituitary. These parts are actually separate glands, each secreting its own hormones.
Pituitary produces hormones which are protein in nature. Their structure has now completely been described. The following are the well known hormones of anterior pituitary.
Growth of human body is affected by many hormones, but the most important role in this complex process is played by pituitary growth hormone (somatropin). After removal of the pituitary, growth of the body virtually stops. Introduction of this hormone accelerates the growth in animals. When a pathological processes leads to a decrease in pituitary function resulting into decreased growth hormone secretion, dwarfism results. These dwarfs have small body, but otherwise they remain normal.
Other disorders of the pituitary gland are characterized by excessive release of growth hormone, resulting into gigantism. If large amounts of growth hormone produced by the body before the maturation of bones is complete, growth increases and a big giant results.
But if it happens after reaching maturity; this results into a condition called acromegaly, in which there is a disproportionate increase in certain parts of the body. This is because the bones in adults lose the ability to further elongate. So, they don’t increase in length but keeps growing resulting into an abnormal shape.
Properties of the growth hormone
- Anabolic effect – promotes muscle growth
- Anti-catabolic effects – slows the process of muscle breakdown
- Decreased appetite
- It reduces the amount of fat in body
- Improves body Energy
- It improves the healing process
- It has a rejuvenating effect
- It stimulates the growth of the internal organs
- It stimulates bone growth and helps increasing the growth in the young age up to 26 years (until the bone keeps growing in length)
- It strengthens bones
- Increases blood glucose
- Enhances immunity
Pituitary (prolactin) stimulates lactation, the formation of milk in the mammary glands. So, it is important for milk production and feeding of the baby. When its levels are raised as in pituitary tumors, persistent lactation combined with amenorrhea (abnormal absence or suppression of menses) may occur. This disorder may also be associated with impaired secretory activity of the hypothalamus, which normally inhibits the release of prolactin. Prolactin is present in the pituitary gland of not only females but also males, and not only in mammals but also in lower vertebrates. We don’t know much about its actions in males. In fish prolactin is involved in the regulation of the osmotic pressure of blood.
Thyroid Stimulating Hormone (TSH)
TSH stimulates the growth of thyroid gland and its secretory activity. After removal of the pituitary gland, thyroid function is completely terminated and it is reduced in size. Introduction of TSH can cause excessive activity of the thyroid gland. Thyroid is important for maintaining basic metabolic rate and various chemical processes being taken place in our body. It is also important for brain growth in infants.
ACTH acts on the adrenal gland and stimulates it, just as thyroid-stimulating hormone stimulates the thyroid gland. The cortex/outer part of adrenal gland secretes hormones known as aldosteron, cortisol and androgens.
- Aldosteron is not under the influence of ACTH and it keeps working even ACTH levels drop. It is important for Sodium re-absorption from kidneys and maintains normal blood pressure.
- Cortisol is under the influence of ACTH and it maintains normal blood sugar levels and prevents hypoglycemia.
- Androgens are important both for females as well as males. They act on axial and groin for axillary or pubic hair development. They also play a role in normal sexual desire in both sexes.
These hormones play an extremely important role in conditions of stress. Without ACTH or a normal functioning adrenal gland, body can’t tolerate stressful conditions and collapses rapidly.
These are the hormones which act on gonads, i.e. ovary and testes. They act on them and stimulate them.
Anterior pituitary secretes two gonadotropin releasing hormones.
- Follicle stimulating hormone (FSH) stimulates the development of eggs in the ovaries and sperm in the testes.
- The second is called luteinizing hormone (LH).In the female body, it stimulates the ovaries to secrete sex hormones and preparation of the egg for fertilization. In men, it stimulates the secretion of male sex hormone known as Testosterone from interstitial cells of the testes.
The excess production of these hormones due to some diseases may cause premature sexual development. When you remove the pituitary gland or it is destructed by some pathological process, the changes that occur are similar to those that occur during castration.