- The pituitary gland, often referred to as the “master gland”, is a small, pea-sized endocrine organ located at the base of the brain, housed within a bony cavity called the sella turcica of the sphenoid bone.
- It lies just below the hypothalamus and is connected to it by a slender stalk known as the infundibulum. Despite its small size—approximately 0.5 grams in adults—the pituitary gland plays a central role in regulating the activity of several other endocrine glands and numerous vital physiological processes.
- The pituitary gland is divided into two main parts: the anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis), which differ in both structure and function. The anterior pituitary originates from oral ectoderm during development and is responsible for producing and secreting several key hormones. These include:
- Growth hormone (GH) – stimulates growth, cell reproduction, and regeneration.
- Thyroid-stimulating hormone (TSH) – promotes thyroid hormone production by the thyroid gland.
- Adrenocorticotropic hormone (ACTH) – stimulates the adrenal cortex to release cortisol and other glucocorticoids.
- Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) – regulate reproductive functions, including ovulation, menstruation, and spermatogenesis.
- Prolactin (PRL) – stimulates milk production in the mammary glands.
- The secretion of these anterior pituitary hormones is controlled by releasing and inhibiting hormones produced by the hypothalamus, which reach the anterior pituitary through a specialized network of blood vessels known as the hypophyseal portal system. This system ensures precise hormonal regulation in response to the body’s changing needs.
- The posterior pituitary, in contrast, is an extension of the hypothalamus and does not produce its own hormones. Instead, it stores and releases two hormones that are synthesized in the hypothalamic neurons and transported down their axons to the posterior lobe:
- Oxytocin – stimulates uterine contractions during labor and milk ejection during breastfeeding; also implicated in social bonding and emotional regulation.
- Antidiuretic hormone (ADH), also known as vasopressin – helps regulate water balance in the body by promoting water reabsorption in the kidneys and constricting blood vessels to raise blood pressure.
- The pituitary gland’s regulatory influence is so profound that it affects nearly every major organ system. It is a central component of several endocrine axes, including the hypothalamic-pituitary-adrenal (HPA) axis, hypothalamic-pituitary-thyroid (HPT) axis, and hypothalamic-pituitary-gonadal (HPG) axis, which are essential for maintaining homeostasis, stress responses, metabolism, growth, reproduction, and development.
- Disorders of the pituitary gland can result in either hypopituitarism (deficiency of one or more pituitary hormones) or hyperpituitarism (excessive hormone production). Common conditions include pituitary adenomas (benign tumors), which may secrete excess hormones (e.g., prolactinomas), or compress surrounding structures, potentially leading to vision problems, headaches, or hormonal imbalances. Other disorders include acromegaly (from excess GH in adults), Cushing’s disease (from excess ACTH), and diabetes insipidus (from ADH deficiency).
