L2.3.1: Pituitary Gland

• PITUITARY GLAND

  ● “Master endocrine gland” because it controls activities of so many other endocrine glands

  ● Pea-sized gland that hangs by a stalk from the hypothalamus in the brain

  ● Location: at the hypophyseal fossa, above sella turcica ○ SELLA TURCICA — “turk’s saddle”; part of the sphenoid bone that protects the pituitary gland
• PITUITARY GLAND

  ● Has 2 functional lobes:

  ○ Anterior pituitary (glandular tissue)

  ○ Posterior pituitary (nervous tissue)

  ● Works hand in hand with the hypothalamus
• POSTERIOR PITUITARY (neurohypophysis)

  ● Does not make the hormones it releases

  ● Stores hormones made by the hypothalamus

  ● Hormones produced: OXYTOCIN and ANTIDIURETIC HORMONE (ADH)
• POSTERIOR PITUITARY (neurohypophysis)

  ○ OXYTOCIN

  ■ Only released in significant amounts during childbirth and nursing

  ■ Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding

  ■ Causes milk ejection (let-down reflex) in a nursing woman

  ■ Acts as a neurotransmitter in the brain: the love hormone
• POSTERIOR PITUITARY (neurohypophysis)

  ○ ANTIDIURETIC HORMONE (ADH)

  ■ Inhibits urine production (diuresis) by promoting water reabsorption by the kidneys

  ■ Urine volume decreases blood volume and pressure increases

  ■ Known as VASOPRESSIN because in large amounts, ADH causes constriction of arterioles, leading to increased BP

  ■ Alcohol inhibits ADH secretion
• ANTERIOR PITUITARY (adenohypophysis)

  ● Produces 6 hormones, all of which are:

  ○ Proteins / peptides

  ○ Regulated by hormonal stimuli

  ○ Regulated mostly by negative feedback
• ANTERIOR PITUITARY (adenohypophysis)

  ● 2 hormones produced affect nonendocrine targets: GROWTH HORMONE (GH) and PROLACTIN (PRL)
• ANTERIOR PITUITARY (adenohypophysis)

  ● 4 tropic hormones produced that stimulate other endocrine glands to release hormones

  ○ FOLLICLE-STIMULATING HORMONE (FSH)

  ○ LUTEINIZING HORMONE (LH)

  ○ THYROTROPIC HORMONE (TH)

  ○ ADRENOCORTICOTROPIC HORMONE (ACTH)
• ANTERIOR PITUITARY (adenohypophysis)

  ○ GROWTH HORMONE (GH) — somatotropin

  ■ General metabolic hormone

  ■ Major effects are directed to growth of skeletal muscles and long bones

  ■ Plays a role in determining final body size

  ■ Causes amino acids to be built into proteins

  ■ Causes fats to be broke down for a source of energy
• ANTERIOR PITUITARY (adenohypophysis)

  ○ PROLACTIN (PRL)

  ■ Stimulates and maintains milk production following childbirth

  ■ Function in males is unknown
• ANTERIOR PITUITARY (adenohypophysis)

  ○ FOLLICLE-STIMULATING HORMONE (FSH)

  ■ A gonadotropic hormone

  ■ Stimulates follicle development in ovaries

  ■ Stimulates sperm development in testes
• ANTERIOR PITUITARY (adenohypophysis)

  ○ LUTEINIZING HORMONE (LH)

  ■ Also a gonadotropic hormone

  ■ Triggers ovulation of an egg in females

  ■ Stimulates testosterone production in males
• ANTERIOR PITUITARY (adenohypophysis)

  ○ THYROTROPIC HORMONE (TH)

  ■ Also called thyroid-stimulating hormone (TSH)

  ■ Influences growth and activity of the thyroid gland
• ANTERIOR PITUITARY (adenohypophysis)

  ○ ADRENOCORTICOTROPIC HORMONE (ACTH)

  ■ Regulates endocrine activity of the adrenal cortex