Pituitary — the Master Gland

Challenges to clear

• Match every hormone and disorder.
• Connect acromegaly to its cause — the timing is what separates it from gigantism.

The task

Connect each pituitary hormone or disorder with what it does or what causes it.

What this lesson covers

• Growth hormone (somatotropin) — Promotes growth of the whole body, particularly the skeleton (Growth hormone from the anterior lobe is essential for normal growth. A dwarf produced by its deficiency is fully developed but retains the body proportions of a child.)
• Thyroid stimulating hormone (TSH) — Activates the thyroid to secrete thyroxine (TSH is a tropic hormone, meaning it acts on another endocrine gland rather than on ordinary body tissue. Tropic simply means influencing the activity of the named organ.)
• Adrenocorticotropic hormone (ACTH) — Regulates the activity of the adrenal cortex (Another tropic hormone of the anterior lobe. Its name spells out its target: adreno-cortico-tropic, aimed at the cortex of the adrenal.)
• Gonadotropic hormones — Regulate the activities of the testes and the ovaries (FSH, LH and prolactin form this group from the anterior lobe. FSH stimulates egg formation in females and sperm formation in males; LH leads to the corpus luteum and to testosterone secretion.)
• Antidiuretic hormone (vasopressin) — Increases reabsorption of water from the kidney tubules (It also constricts blood vessels, raising blood pressure. Its deficiency causes diabetes insipidus, where urination is frequent and copious but the urine contains no sugar.)
• Oxytocin — Contracts the uterus at childbirth and stimulates milk ejection (Its Greek name means quick childbirth. It comes from the posterior lobe, and uterine contraction is the standard example of positive feedback in the body.)
• Gigantism — Oversecretion of growth hormone during childhood (While the long bones can still lengthen, excess growth hormone makes them grow beyond normal, producing human giants of up to 2.7 metres.)
• Acromegaly — Oversecretion of growth hormone after growth is complete (In an adult the long bones can no longer lengthen, so the excess causes overgrowth of the bones of the face, especially the jaws, and of the hands and feet, with a large nose and thick lips.)

Hint

The pituitary is called the master gland because its tropic hormones control the other endocrine glands, yet it is only the size of a pea seed and hangs below the hypothalamus. ADH and oxytocin come from the POSTERIOR lobe; growth hormone and all the tropic hormones come from the ANTERIOR lobe.