THE PITUITARY GLAND
Topic: The Endocrine System
Next Unit: The Thyroid Gland
6 minute read
The pituitary gland, often called the "master" gland, secretes hormones that control many other endocrine glands in the body. It can be divided into the posterior pituitary and the anterior pituitary.
The posterior pituitary gland stores two hormones until they are needed. One of these hormones is antidiuretic hormone (ADH), also known as vasopressin. ADH is released in response to changes in the osmotic pressure of the blood, as detected by osmoreceptors in the hypothalamus. Its main function is to regulate water balance by causing the kidneys to reabsorb water instead of excreting it as urine. If the osmolality of the blood is too high, ADH helps to restore it to normal levels.
The other hormone stored in the posterior pituitary is oxytocin. Oxytocin is released when the electrical activity of oxytocin cells in the hypothalamus is stimulated. Its primary role is to facilitate childbirth by causing uterine contractions in females. Additionally, oxytocin plays a role in milk ejection during lactation and can decrease urine output. It is also associated with empathy and influences certain moods and behaviors.
The anterior pituitary gland releases six main hormones, including
GROWTH HORMONE: a peptide that stimulates growth in children and adults alike and promotes cell changes such as reproduction and regeneration.
THYROID-STIMULATING HORMONE (TSH): an amine responsible for the metabolism of almost every tissue in the body through its action on the thyroid.
ADRENOCORTICOTROPIC HORMONE (ACTH): a peptide responsible for increased production and release of cortisol and affects the human sleep cycle (circadian rhythm).
PROLACTIN: a protein that stimulates the mammary glands to produce milk (lactation), plays a role in sexual activity, and stimulates the creation of myelin coatings on axons and the pulmonary surfactant in the lungs of newborns.
FOLLICLE-STIMULATING HORMONE (FSH): a peptide responsible for the development, growth, puberty, and reproductive processes. It stimulates the egg follicles in the ovaries to begin maturation toward ovulation.
LUTEINIZING HORMONE (LH): a protein responsible for developing secondary sexual characteristics in both males and females by releasing progesterone and testosterone, respectively. LH is also responsible for ovulation, the process of egg release from the ovaries.
The pituitary gland also secretes endorphins, chemicals that reduce the feeling of pain by activating the body's opiate receptors, resulting in a significant analgesic effect.