Endocrine pt.2

Endocrine Glands Recap

  • Major Endocrine Glands

    • Importance of understanding the hypothalamus as a regulator.

    • Focus on the pituitary gland and its two parts:

    • Anterior Pituitary: Produces hormones in response to hypothalamic releasing hormones.

    • Posterior Pituitary: Acts primarily as a storage center for hormones produced in the hypothalamus.

Hormones of the Anterior Pituitary

  • Hormones Produced:

    • Major hormones include:

    • Growth Hormone (GH): Secreted by somatotroph cells.

    • Adrenocorticotropic Hormone (ACTH): Targets the adrenal gland.

    • Thyroid Stimulating Hormone (TSH): Targets the thyroid.

  • Somatotrophs:

    • Found in the anterior pituitary and responsible for secreting growth hormone.

  • Corticotropin Releasing Hormone (CRH):

    • Released by the hypothalamus to regulate ACTH secretion.

  • Negative Feedback Mechanism:

    • Elevated cortisol levels inhibit the release of CRH, consequently decreasing ACTH and maintaining homeostasis.

Regulation of Thyroid Hormones

  • Thyroid Regulation:

    • Thyrotropin Releasing Hormone (TRH) from the hypothalamus stimulates TSH production in the anterior pituitary.

    • Negative feedback mechanism applies where high thyroid hormone levels inhibit TRH release.

  • FSH and LH (Gonadotropins):

    • Gonadotropins produced in response to Gonadotropin Releasing Hormone (GnRH).

    • Follicle Stimulating Hormone (FSH): Activates ovarian follicles; produces eggs in females and sperm in males.

    • Luteinizing Hormone (LH): Stimulates hormone production in reproductive organs.

Prolactin: Production and Regulation

  • Prolactin:

    • Primarily targets breast tissue to stimulate milk production.

  • Oxytocin vs. Prolactin:

    • Prolactin stimulates milk secretion, while oxytocin is responsible for milk letdown.

  • Regulation of Prolactin:

    • PIH (Prolactin Inhibiting Hormone) from the hypothalamus prevents excess prolactin production.

  • Regulatory Fluctuations:

    • Elevated estrogen levels during pregnancy reduce PIH, allowing prolactin levels to rise.

    • Minor fluctuations in prolactin prior to menstruation without significant effects on histology.

  • Contraceptive and Health Issues:

    • Excessively high prolactin can lead to conditions like galactorrhea.

Adrenal Gland Anatomy and Function

  • Adrenal Gland Structure:

    • Composed of two distinct parts:

    • Adrenal Cortex: Produces corticosteroids (mineralocorticoids and glucocorticoids).

    • Adrenal Medulla: Produces epinephrine and norepinephrine.

  • Corticosteroids:

    • Mineralocorticoids: Key hormone is Aldosterone.

    • Glucocorticoids: Key hormone is Cortisol.

Cortisol Functions and Effects

  • Cortisol Functions:

    • Stimulates gluconeogenesis, increasing glucose levels in response to stress.

    • Regulates metabolism, affects immune response, and promotes tissue repair.

    • Uses fats and protein breakdown as an energy source during stress.

  • Negative Feedback in Cortisol Regulation:

    • Elevated cortisol levels inhibit ACTH and CRH production, preventing excessive cortisol production.

Clinical Correlations

  • Cushing's Syndrome:

    • Elevated cortisol due to pituitary tumors causing continual ACTH production.

    • Symptoms: Fat deposition (buffalo hump, moon face) and hypertension.

  • Treatment for Cushing's:

    • Typically involves surgical tumor removal.

Summary of Hormonal Interactions

  • Hormonal axes involving the hypothalamus, anterior pituitary, and target endocrine glands.

  • Importance of understanding interactions for maintaining hormonal balance and overall physiological health.