Pituitary Gland: Functions, Hormones, and Pathophysiology
Pituitary Gland: Functions and Hormones
The pituitary gland, also known as the hypophysis, is a gland located at the base of the brain. It plays a crucial role in regulating other glands. The pituitary gland is divided into two main parts:
Anterior Lobe (Adenohypophysis)
The anterior lobe produces several hormones that stimulate other glands to secrete their hormones. These include:
- TSH (Thyroid-Stimulating Hormone): Stimulates the thyroid gland to produce T3 and T4, which regulate metabolism.
- FSH (Follicle-Stimulating Hormone): Controls the maturation of ovarian follicles and sperm.
- LH (Luteinizing Hormone): Stimulates the secretion of the corpus luteum in women and testosterone in men.
- ACTH (Adrenocorticotropic Hormone): Activates the secretion of hormones from the adrenal cortex.
- STH or GH (Growth Hormone): Promotes growth throughout the body.
- LTH (Luteotrophic or Prolactin Hormone): Stimulates milk secretion in the breasts.
Intermediate Lobe
The intermediate lobe produces:
- MSH (Melanocyte-Stimulating Hormone): Favors the synthesis of melanin.
Posterior Lobe (Neurohypophysis)
The posterior lobe does not synthesize hormones but stores and releases them. These include:
- ADH (Antidiuretic Hormone or Vasopressin): Concentrates urine in the kidneys, preventing excessive water loss.
- Oxytocin: Contracts the myometrium, causing childbirth and milk ejection.
Pathophysiology of Diabetes Mellitus
The lack of glucose causes cells to accumulate in the blood (hyperglycemia). Glucose is eliminated in the urine (glycosuria), and glucose drags a large amount of water from the kidney (polyuria). Due to the loss of water, there is a sensation of thirst (polydipsia), and because glucose is not used, the person feels hunger (polyphagia).
Diabetes Mellitus
There are two main types of diabetes:
- Type I Diabetes (Juvenile IDDM): Hyposecretion of insulin. It typically appears at puberty or before age 40. It is not hereditary. The onset is acute, with polyuria, polydipsia, polyphagia, and ketoacidosis. Treatment involves exogenous insulin for life. Complications include microvascular and neuropathies.
- Type II Diabetes (NIDDM): Insulin is produced normally or is high but ineffective. It appears after age 40, often runs in families, and is often associated with being overweight. It is diagnosed through a routine blood test or the appearance of polyuria, polydipsia. Ketoacidosis is rare. Treatment includes diet, exercise, and oral antidiabetic medications. Complications include coronary artery disease, stroke, and peripheral vascular diseases.
Other Types of Diabetes
- Secondary Diabetes: Caused by conditions like pancreatitis or certain medications.
- Gestational Diabetes: Occurs during pregnancy.
Acute and Chronic Complications of Diabetes
Acute Complications
- Ketoacidosis: Characterized by hyperglycemia.
- Hypoglycemia: Common, especially in the elderly.
- Hyperosmolar Coma: A serious condition.
Chronic Complications
- Arteriosclerosis: Affects arteries throughout the body.
- Microvascular Abnormalities: Retinopathy and renal disease.
- Macrovascular Diseases: Coronary artery disease, cerebrovascular disease, and peripheral vascular disease.
- Neuropathies: Affecting cranial sensory and motor nerves.
The Gonads
The gonads are the ovaries and testes.
- Luteinizing Hormone (LH): Stimulates the ovaries to secrete the corpus luteum.
- Follicle-Stimulating Hormone (FSH): Stimulates the ovaries to mature the ovum and the testicles to produce spermatids.