Skip to main content
Back

physiology ch 23 endocrine

NotesPracticeVideo lessons

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Chapter 23: Endocrine Control of Growth and Metabolism

23.1 Review of Endocrine Principles

The endocrine system regulates physiological processes through hormones secreted by glands. These hormones travel via the bloodstream to target organs, influencing growth, metabolism, and homeostasis.

  • Hypothalamic-pituitary control system: The hypothalamus and pituitary gland coordinate the release of many hormones.

  • Feedback patterns: Negative and positive feedback loops regulate hormone levels.

  • Cellular mechanism of action: Hormones bind to specific receptors, triggering cellular responses.

  • Endocrine pathologies: Disorders arise from hormone excess, deficiency, or abnormal responsiveness.

23.2 Adrenal Glucocorticoids

Glucocorticoids are steroid hormones produced by the adrenal cortex, with cortisol being the primary glucocorticoid in humans.

  • Functions: Regulate metabolism, immune response, and stress adaptation.

  • Secretion: Controlled by the hypothalamic-pituitary-adrenal (HPA) axis.

  • Key hormones: Cortisol, aldosterone (mineralocorticoid), and androgens.

Cortisol Secretion and Regulation

  • ACTH (Adrenocorticotropic hormone): Stimulates cortisol release from the adrenal cortex.

  • HPA Axis: Hypothalamus releases CRH (corticotropin-releasing hormone) → Pituitary releases ACTH → Adrenal cortex releases cortisol.

Equation:

Functions of Cortisol

  • Essential for life; maintains homeostasis during stress.

  • Promotes gluconeogenesis, protein catabolism, and lipolysis.

  • Suppresses immune response and inflammation.

  • Influences calcium balance and brain function.

Cortisol Pathologies

  • Hypersecretion: Cushing's syndrome (characterized by obesity, muscle weakness, and skin changes).

  • Hyposecretion: Addison's disease (fatigue, weight loss, hypotension).

23.3 Thyroid Hormones

Thyroid hormones regulate metabolism, growth, and development. The thyroid gland produces thyroxine (T4) and triiodothyronine (T3).

  • TSH (Thyroid-stimulating hormone): Controls thyroid hormone synthesis and release.

  • Functions: Increase metabolic rate, promote protein synthesis, and are essential for normal growth and development.

Thyroid Hormone Synthesis

  • Iodine is required for synthesis.

  • Thyroglobulin is the precursor protein.

  • Enzymatic reactions in the thyroid follicle produce T3 and T4.

Thyroid Pathologies

  • Hyperthyroidism: Excess thyroid hormone (Graves' disease, goiter).

  • Hypothyroidism: Deficient thyroid hormone (Hashimoto's disease, cretinism).

  • Symptoms: Weight changes, altered heart rate, skin and hair changes, and developmental delays in children.

Table: Thyroid Hormones and Effects

Hormone

Main Effect

T3 (Triiodothyronine)

Increases metabolic rate, protein synthesis

T4 (Thyroxine)

Precursor to T3, similar effects

TSH

Stimulates thyroid hormone production

Additional info:

Table inferred from slide content

23.4 Growth Hormone

Growth hormone (GH) is essential for normal growth and metabolism. It is secreted by the anterior pituitary and acts on various tissues.

  • Functions: Stimulates protein synthesis, increases fat breakdown, and promotes bone and tissue growth.

  • Regulation: Controlled by GHRH (growth hormone-releasing hormone) and somatostatin from the hypothalamus.

  • Feedback: GH secretion is regulated by negative feedback from IGF-1 (insulin-like growth factor 1).

Equation:

Growth Hormone Pathologies

  • Excess: Gigantism (children), acromegaly (adults).

  • Deficiency: Dwarfism, poor growth.

23.5 Tissue and Bone Growth

Bone and tissue growth require coordinated hormonal control and adequate nutrition.

  • Key factors: GH, IGF-1, thyroid hormones, and sex steroids.

  • Bone growth: Involves osteoblast activity and matrix synthesis.

  • Dietary calcium: Essential for bone mineralization.

23.6 Calcium Balance

Calcium is vital for cellular function, bone health, and blood clotting. Its levels are tightly regulated by hormones.

  • Distribution: Most calcium is stored in bones; plasma calcium is regulated.

  • Regulatory hormones: Parathyroid hormone (PTH), calcitriol (vitamin D), and calcitonin.

Table: Hormonal Control of Calcium Balance

Hormone

Source

Main Effect

PTH

Parathyroid gland

Increases plasma Ca2+ by stimulating bone resorption and kidney reabsorption

Calcitriol

Kidney (activated vitamin D)

Increases intestinal absorption of Ca2+

Calcitonin

Thyroid gland

Lowers plasma Ca2+ by inhibiting bone resorption

Summary Table: Major Endocrine Axes in Growth and Metabolism

Axis

Key Hormones

Main Functions

HPA Axis

CRH, ACTH, Cortisol

Stress response, metabolism, immune regulation

Thyroid Axis

TRH, TSH, T3/T4

Metabolism, growth, development

GH Axis

GHRH, GH, IGF-1

Tissue and bone growth, protein synthesis

Calcium Regulation

PTH, Calcitriol, Calcitonin

Bone health, plasma calcium balance

Key Terms and Definitions

  • Glucocorticoids: Steroid hormones from the adrenal cortex, mainly cortisol.

  • Thyroid hormones: T3 and T4, regulate metabolism and growth.

  • Growth hormone (GH): Anterior pituitary hormone promoting growth and metabolism.

  • Parathyroid hormone (PTH): Regulates plasma calcium levels.

  • Calcitriol: Active form of vitamin D, increases calcium absorption.

  • Calcitonin: Lowers plasma calcium levels.

Examples and Applications

  • Cushing's syndrome: Example of glucocorticoid excess.

  • Graves' disease: Example of hyperthyroidism.

  • Acromegaly: Example of excess growth hormone in adults.

  • Osteoporosis: Example of calcium imbalance affecting bone health.

Additional info: Academic context and table entries inferred from slide structure and standard physiology content.

Pearson Logo

Study Prep