Endocrine System – Review of Organs, Tissues, and Main Functions

Purpose of the Review

• To familiarize students with the location and primary functions of these tissues.
• To understand potential consequences of endocrine diseases or endocrine gland damage, which typically result in either:
  • Reduced hormone production
  • Excess hormone production

Overview of Endocrine Organs and Tissues

This section reminds us of the key endocrine organs and tissues within the human body:

The Hypothalamus: The Control Center

• Located in the brain, it is regarded as the ‘control center’ of the endocrine system.
• Hypothalamus:  Produces two primary hormones independently:
  • ADH (Antidiuretic Hormone): Regulates fluid and water balance in blood and tissues.
  • Oxytocin (OXT): Released during childbirth to stimulate uterine contractions.

Hypothalamus: Regulatory Role

• Produces regulatory hormones that control the pituitary gland, especially the anterior pituitary.
• These hormones act as signals that regulate hormone secretion in the pituitary.

Hormones Produced by the Hypothalamus

• ADH (Antidiuretic hormone): Maintains water-salt balance.
• Oxytocin (OXT): Facilitates uterine contractions during delivery.
• Regulatory hormones: Control secretion of anterior pituitary hormones.

The Pituitary Gland: The “Workhorse”

• Located just below the hypothalamus.
• Produces many hormones in response to hypothalamic regulatory hormones.
• Divided into two lobes:
  • Anterior lobe:
    • Responds to regulatory hormones from the hypothalamus.
    • Produces and releases several hormones.
  • Posterior lobe:
    • Stores and releases hormones synthesized by the hypothalamus (e.g. ADH and oxytocin).

Anatomical Context

• The hypothalamus is situated above the pituitary gland in the brain.
• The anterior and posterior pituitary are distinct but connected regions.

Anterior Pituitary Hormones

The anterior pituitary produces and releases the following hormones:

1. ACTH (Adrenocorticotropic hormone): Stimulates adrenal cortex to produce cortisol.
2. TSH (Thyroid-stimulating hormone): Stimulates the thyroid gland to produce thyroid hormones.
3. GH (Growth hormone): Promotes growth of tissues and organs.
4. PRL (Prolactin): Stimulates milk production in the breasts.
5. FSH (Follicle-stimulating hormone): Involved in reproductive processes, including ovarian follicle development and sperm production.
6. LH (Luteinizing hormone): Triggers ovulation and stimulates testosterone production.
7. MSH (Melanocyte-stimulating hormone): Regulates pigmentation in the skin.

Posterior Pituitary Hormones

are produced by the Hypothalamus but released from posterior pituitary

• OXT (Oxytocin):
• ADH (Antidiuretic Hormone):

Summary

This review provides a foundational understanding of the primary organs of the endocrine system, their hierarchical control, and the hormones responsible for vital physiological processes. The hypothalamus acts as the master regulator, while the pituitary gland functions as a central output organ producing multiple hormones essential for growth, metabolism, reproduction, and homeostasis.