Table of Contents
Introduction:
The pituitary gland is one of the major glands in the human body. It appears to be the size of a small pea between the brain lobes. The pituitary gland involves various body functions, including growth, development, and sexuality. The gland is also known as the hypophysis and consists of two lobes: the anterior and posterior pituitary lobes. Each lobe has an individual function and control in maintaining the body.
What Is the Structure of the Anterior Pituitary Gland?
The anterior pituitary, also known as adenohypophysis, is one of the pituitary gland's two lobes, situated in the sella turcica (a depression present in the sphenoid bone) and regulated by the hypothalamus. The anterior pituitary consists of the following parts:
-
Pars Tuberalis: A highly vascular sheath that extends from the distal surface (pars distalis) from the anterior lobe and wraps around the pituitary stalk. This area is occupied by epithelial cells organized in cords and portal arteries supplying the pituitary.
-
Pars Intermedia: This is a tissue section between the posterior pituitary and the pars distalis. This region of the anterior pituitary is made up of pale, big cells. The cells of the pars intermedia contain follicles with a colloidal matrix. The major hormone released by this region of the anterior pituitary is MSH, also known as the melanocyte-stimulating hormone (a hormone responsible for skin pigmentation and helps protect the skin from UV rays).
What Are the Functions of the Anterior Pituitary Gland?
The pituitary gland performs various activities because it is the body's most important organ. The pituitary gland has several roles, including:
-
Provides energy to the body and its bodily functions.
-
It helps in reproduction and breastfeeding by acting on the sexual organs.
-
It is responsible for growth and height management.
-
Manages and regulates blood pressure.
-
Maintains the body's water-salt balance while activating the kidneys.
-
Maintains UV protection and the color of the skin.
-
Promotes the development of sexual organs.
-
Increases the body's metabolism.
-
Balances the level of stress hormones.
What Are the Anterior Pituitary Hormones?
The anterior pituitary gland is a small glandular structure present in the front of the pituitary gland and holds around six major functions of the pituitary gland. All these functions of the pituitary gland uphold major bodily functions and their nature. Here, the hormones of the anterior pituitary gland include:
-
Adrenocorticotropic Hormone (ACTH): Adrenocorticotropic hormone (ACTH) is released in reaction to corticotropin-releasing hormone (CRH) from the pituitary gland. The CRH would go from the hypothalamus to the veins and end capillaries (portal system). When it reaches the anterior pituitary gland, it induces the division of proopiomelanocortin (POMC) (the precursor to skin pigmentation or the melanin hormone) into several molecules. Here, the three main hormones are ACTH, melanocyte-stimulating hormone (MSH), and beta-endorphins (the proteins involved in the processing and management of pain). During this process, ACTH enters the circulation and activates the adrenal cortex, or the outer portion of the adrenal gland, helping produce cortisol (the stress hormone). The activation of cortisol also provides negative feedback by inhibiting the release of CRH and ACTH.
-
Follicle Stimulating Hormone (FSH): The anterior pituitary gland's gonadotropic cells (cells found in both male and female reproductive organs) produce the FSH hormone. In women, FSH stimulates the ovaries to produce steroid hormones. FSH increases the follicular growth of the ovary in women, and this helps in maturity and reproduction. In males, FSH stimulates the Leydig cells in the testes to release testosterone and the Sertoli cells to secrete androgen-binding proteins, which aid in commencing sperm production. However, in both males and females, these hormones help mature primordial germ cells (undifferentiated stem cells), eventually developing into eggs or sperms.
-
Growth Hormone: Growth hormone affects many tissues and enhances their development. Some of them are:
-
Growth hormone promotes the growth of many different tissues.
-
Growth hormone promotes the production of proteins, which in turn promotes growth linearly.
-
GH stimulates the liver and other organs to produce more somatomedins and enhances the transfer of amino acids between cells.
-
Somatomedin promotes the division and growth of cells.
-
Boost the growth of T lymphocytes.
-
The intestines absorb more calcium, but the excreted urine decreases visibly.
-
It elevates blood sugar levels by causing the breakdown of sugar enzymes (glycogen) in the liver and also encourages the growth of bone and other soft tissue components.
-
Boost the amount of unmetabolized fatty acids absorbed by the muscles.
-
Growth hormone-releasing hormone (GHRH) is released by the cerebral cortex and interacts with anterior pituitary gland cells.
-
-
Prolactin: The anterior pituitary gland controls prolactin, the hormone responsible for milk production and breast development. Dopamine (a chemical messenger of the brain) is the primary hormone that inhibits prolactin release. When the anterior pituitary gland receives signals from the afferent sensory nerve cell input from nursing women's nipples, the feedback loop that receives the signal in the brain inhibits the prolactin reversal, thus releasing milk. Suckling also sends a message to the brain that prevents dopamine release. These factors create an unopposed release of prolactin, the feeding hormone that promotes breast growth and development and maintains breastfeeding in women.
-
Luteinizing Hormone: These two hormones are produced by the gonadotrophin cells in the anterior pituitary gland. With its effects on the luteinizing hormone in the ovaries, it accelerates steroid production in women. However, in men, the luteinizing hormone (LH), which is present, releases testosterone from the Leydig cells in the testes, which is the primary hormone responsible for the sexual behavior of men. In both males and females, these hormones support the formation of primordial stem cells.
-
Thyroid Stimulating Hormone (TSH): After the pituitary, the thyroid gland plays a very important role, as do the thyroid hormones. Three thyroid hormones are present, namely T3, T4, and TSH. Here, the purpose of TSH is to stimulate the thyroid gland's functions and ensure adequate production and release of triiodothyronine T3 and thyroxine T4 hormones.
Conclusion:
The anterior pituitary gland, also called adenohypophysis, is one of the significant endocrine glands, producing and secreting several vital hormones that control several important processes in the human body. The anterior pituitary cannot be underestimated, considering the range of the secreted hormones it supplies when needed for metabolism, growth, stress response, and reproduction. However, by releasing and inhibiting hormones, the brain creates a complex feedback loop that balances the hormones and allows only a normal physiological condition. Any disease of the anterior pituitary may lead to serious effects on health, like GH imbalance resulting in dwarfism or gigantism; deficiency of TSH leading to hypothyroidism (decrease in thyroid levels); and imbalance of the gonadotropins or sexual hormones affecting reproductive health. Because of this, understanding the anterior pituitary is essential for overall health and wellness.
