Overview
This lecture covers the hypothalamus and pituitary gland, their hormones, and how these hormones regulate key body functions through direct and indirect mechanisms.
Major Glands of the Endocrine System
- The main endocrine glands include the hypothalamus, pituitary, pineal, thyroid, thymus, adrenal glands, pancreas, ovaries, and testes.
- Today's focus is on the hypothalamus and pituitary gland; other glands will be covered next week.
Hypothalamus and Pituitary Gland Relationship
- The hypothalamus and pituitary gland are connected via the infundibulum (a stalk of tissue).
- The pituitary gland is divided into anterior and posterior lobes.
- The hypothalamus produces hormones that are stored and/or released by the pituitary gland.
Posterior Pituitary Hormones
- Posterior pituitary stores and releases oxytocin and antidiuretic hormone (ADH/vasopressin), both made in the hypothalamus.
- Oxytocin stimulates uterine contractions during childbirth and milk let-down during breastfeeding.
- ADH is released when dehydrated, targets the kidneys to retain water, and results in concentrated (darker) urine.
- Hydration state controls the release of ADH and kidney water retention.
Anterior Pituitary Hormones
- The anterior pituitary is called the "master gland" and makes six major hormones.
- Tropic hormones stimulate other glands to secrete their hormones; non-tropic hormones act directly on tissues.
- Non-tropic: Growth hormone (GH) and prolactin.
- Tropic: Thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH).
Hormone Functions and Pathways
- GH stimulates growth, especially of bone and muscle, by raising blood levels of protein, glucose, and fatty acids.
- Prolactin stimulates milk production in breastfeeding women.
- TSH stimulates the thyroid gland to release thyroid hormones (T3, T4); regulated by TRH from the hypothalamus and feedback inhibition.
- ACTH stimulates adrenal glands to release cortisol, aldosterone, and sex hormones, especially during stress.
- FSH and LH (gonadotropins) regulate reproductive processes in both men and women, including hormone production and gamete maturation.
Key Terms & Definitions
- Hypothalamus — Brain region controlling pituitary hormone release.
- Pituitary gland — Master endocrine gland beneath the brain.
- Infundibulum — Stalk connecting hypothalamus and pituitary.
- Anterior Pituitary (Adenohypophysis) — Front lobe producing six major hormones.
- Posterior Pituitary (Neurohypophysis) — Back lobe releasing oxytocin and ADH.
- Tropic hormone — Hormone that stimulates another gland to release a hormone.
- Oxytocin — Hormone for labor contractions and milk letdown.
- Antidiuretic Hormone (ADH) — Hormone controlling kidney water reabsorption.
- Growth Hormone (GH) — Stimulates growth and metabolism.
- Thyroid-stimulating hormone (TSH) — Stimulates thyroid hormone release.
- Adrenocorticotropic hormone (ACTH) — Stimulates adrenal hormone release.
- Follicle-stimulating hormone (FSH) — Regulates gamete production.
- Luteinizing hormone (LH) — Stimulates ovulation/testosterone production.
- Feedback inhibition — Process where rising hormone levels suppress further release.
Action Items / Next Steps
- Review these notes for understanding of hormone pathways and feedback mechanisms.
- Prepare for a deeper discussion on the thyroid gland and its hormones next week.
- Email any questions for clarification or further examples.