Endocrinology: Pituitary Gland Functions

Pituitary Gland

• The pituitary gland's primary function is to regulate and control various bodily functions through the production and release of hormones.
• Somatotrophic cells secrete growth hormone (GH), also known as somatotropin.
• The pituitary gland is roughly the size of a pea, measuring about 1 cm in diameter.
• The anterior pituitary, responsible for secreting a variety of hormones, makes up about 75% of the pituitary gland's total weight.
• The pituitary gland connects to the hypothalamus through a stalk-like structure called the infundibulum.
• The hypothalamus plays a crucial role in regulating various bodily activities, including appetite, sleep, body temperature, and hormone secretion.
• The posterior pituitary is primarily composed of nervous tissue.
• The pars intermedia, a region of the pituitary gland, ceases to exist in adults.

Hypothalamus and Pituitary Hormone Regulation

• The hypothalamus, a brain region, regulates a wide range of bodily functions, including growth, reproduction, and metabolism, through the production and release of hormones that control the pituitary gland.
• Thyrotrophic cells secrete thyroid-stimulating hormone (TSH), which controls the thyroid gland's activity.
• In men, Follicle Stimulating Hormone (FSH) stimulates sperm production in the testes.
• The posterior pituitary stores and releases two hormones: Antidiuretic Hormone (ADH) and oxytocin.
• Antidiuretic Hormone (ADH) increases water reabsorption in the kidneys, thereby reducing urine production.
• Inhibin, produced by the gonads, inhibits the secretion of FSH.
• The ovaries produce estrogen, a hormone responsible for regulating the menstrual cycle.
• Prolactin stimulates milk production in mammary glands.
• Corticotrophic cells secrete Adrenocorticotropic Hormone (ACTH).
• In males, testosterone plays a crucial role in the development and maintenance of male sexual characteristics, including muscle growth, deepening of the voice, and sperm production.
• In women, Luteinizing Hormone (LH) triggers ovulation (release of an egg from the ovary) and stimulates the production of hormones like progesterone.
• Relaxin, secreted during pregnancy, relaxes the ligaments and muscles in the pelvic area, aiding in childbirth.

Ovaries and Hormones

• The ovaries produce estrogen, progesterone, and relaxin.
• Oxytocin, produced in the hypothalamus and released by the posterior pituitary gland, triggers uterine contraction during labor and milk ejection after birth.
• Adrenocorticotropic Hormone (ACTH) stimulates the adrenal cortex to secrete glucocorticoids, hormones essential for managing stress and regulating blood sugar levels.

Gametes and Gonadotropins

• Gametes (sex cells) are produced in the gonads, which include the testes in males and the ovaries in females.
• Melanocyte Stimulating Hormone (MSH) is secreted by melanotroph cells, which are located in the anterior pituitary gland..

Parathyroid Glands and Calcium Regulation

• The parathyroid glands, typically four small glands located near the thyroid gland, secrete parathyroid hormone (PTH).
• Parathyroid hormone (PTH) plays a crucial role in regulating calcium levels in the blood, promoting calcium absorption in the digestive system, and increasing calcium release from bones.
• The parathyroid glands are closely associated with the thyroid gland.

Suprarenal Cortex and Hormone Production

• The zona glomerulosa, the outermost layer of the suprarenal cortex, primarily secretes mineralocorticoids, such as aldosterone, which regulate electrolyte balance and blood pressure.
• The zona fasciculata, a middle layer of the suprarenal cortex, produces glucocorticoids, such as cortisol, which are essential for managing stress and regulating blood sugar levels.

Parathyroid and Suprarenal Glands

• Parathyroid glands are typically about 3-5 mm in size.
• Excessive levels of thyroid hormone mainly affect metabolism, potentially leading to hyperthyroidism, a condition characterized by increased metabolic activity.
• Parathyroid hormone elevates blood calcium levels by stimulating bone resorption, a process where bone tissue is broken down to release calcium into the bloodstream.

Oxytocin and Childbirth

• Oxytocin plays a crucial role during delivery by stimulating uterine contraction and promoting milk ejection after childbirth.
• In the absence of antidiuretic hormone (ADH), urine output increases significantly due to reduced water reabsorption in the kidneys.

Thyroid Gland and its Function

• The thyroid gland, a butterfly-shaped gland located in the neck, is responsible for producing thyroid hormones, namely triiodothyronine (T3) and thyroxine (T4), which regulate metabolism and are essential for growth and development.
• Alcohol inhibits the release of antidiuretic hormone (ADH), leading to increased urine production and dehydration.
• The thyroid gland typically weighs about 15-20 grams.
• After delivery, oxytocin plays a vital role in promoting bonding between mother and child through its effects on social interaction and emotional connection.
• An isthmus, a narrow strip of tissue, connects the two lobes of the thyroid gland.

Hormonal Function

• Aside from its roles in childbirth and breastfeeding, oxytocin potentially contributes to social bonding and emotional regulation in males and non-pregnant females.
• The kidneys are responsible for regulating blood volume and composition, including reabsorbing water back into the bloodstream.