CHAPTER 13- ENDOCRINE SYSTEM DISORDER updated

Endocrine System Disorders

Learning Objectives

• Understand the Hypothalamus-Pituitary hormonal axis.

• Explain the causes, symptoms, and tests for each endocrine disorder:

  • Growth Disorders

  • Thyroid Disorders

  • Adrenal Disorders

• Elaborate on each Dynamic Function Test.

Overview of the Endocrine System

• Comprises various glands throughout the body.

• Regulates numerous bodily functions by releasing hormones into the bloodstream.

• Hormones influence other glands or body systems and are transported via blood to target tissues.

Endocrine Disorders

• Hormone Deficiency (Hyposecretion):

  • Inadequate hormone production or sensitivity.

• Hormone Excess (Hypersecretion):

  • Excessive hormone production or sensitivity.

• Hormone Resistance:

  • Body's tissues do not respond appropriately to hormones.

Mechanisms of Endocrine Diseases

Deficiency

• Caused by:

  • Destructive processes in hormone-producing glands (e.g., infection, tumors).

  • Genetic defects in hormone production (e.g., congenital adrenal hyperplasia).

  • Mutations in hormone receptors (e.g., Testicular Feminization Syndrome).

Excess

• Caused by:

  • Overproduction by endocrine glands or ectopic tissues (e.g., tumors).

  • External factors like excessive medication (e.g., anabolic steroids).

• Grave’s Disease: Anti-receptor antibodies stimulate excessive hormone production.

• Type II Diabetes: Reduced receptor function due to excess hormone levels.

Hypothalamus and Pituitary

• Dominant part of the endocrine system, regulating thyroid, adrenal, and reproductive glands.

• Controls growth, lactation, and water metabolism.

Hypothalamic Releasing Hormones

• Corticotropin Releasing Hormone (CRH): Stimulates ACTH secretion.

• Thyrotropin Releasing Hormone (TRH): Stimulates TSH and Prolactin secretion.

• Growth Hormone Releasing Hormone (GHRH): Stimulates GH secretion.

• Somatostatin: Inhibits GH and other hormone secretion.

• Gonadotropin Releasing Hormone (GnRH): Stimulates LH and FSH secretion.

• Prolactin Releasing Hormone (PRH): Stimulates PRL secretion.

• Prolactin Inhibiting Hormone (Dopamine): Inhibits PRL secretion.

Anterior Pituitary Hormones

• GH (Growth Hormone): Stimulates growth in liver and other organs.

• FSH (Follicle Stimulating Hormone): Regulates ovarian and testicular function.

• LH (Luteinizing Hormone): Stimulates ovulation and testosterone production.

• TSH (Thyroid Stimulating Hormone): Stimulates thyroid hormone synthesis.

• ACTH (Adrenocorticotropic Hormone): Stimulates cortisol production in adrenal cortex.

• Prolactin: Promotes milk production in the breast.

Posterior Pituitary Hormones

• Oxytocin: Controls uterine contraction and milk release.

• Vasopressin (ADH): Regulates water balance; excess leads to water retention, deficiency leads to dehydration.

Hypothalamus-Pituitary Endocrine Diseases

Hypopituitarism

• Clinical manifestations vary by age:

  • Infants: growth disorders

  • Women: amenorrhea and infertility

  • Men: reduced libido

  • Older adults: hormonal deficiencies leading to hypoglycemia.

Diabetes Insipidus

• Caused by low/no ADH leading to excessive thirst and dehydration.

Growth Hormone Disorders

Excess Growth Hormone

• In children: Gigantism leading to excessive height.

• In adults: Acromegaly causes tissue enlargement after puberty.

Hyposecretion of GH

• Results in dwarfism.

• Controlled by GHRH, somatostatin, and ghrelin.

Acromegaly and Gigantism

• Increased GH secretion leads to coarse facial features, enlarged body organs, and abnormal menstruation.

Hyperprolactinemia

• Increased prolactin in plasma.

• Women: menstrual issues and infertility.

• Men: hypogonadism and reduced libido.

Disorders of Adrenal Gland

Hypothalamus-Pituitary-Adrenal Axis

• Cortisol production regulated by CRH and ACTH.

Adrenal Cortex Function

• Produces glucocorticoids, mineralocorticoids, and androgens.

Addison’s Disease

• Causes low cortisol levels, can be primary (direct loss of gland function) or secondary (decreased ACTH from pituitary).

• Symptoms include weight loss, fatigue, skin pigmentation changes, low blood pressure, and hyperkalemia.

Cushing’s Syndrome

• Caused by elevated cortisol levels, often due to corticosteroid use or tumors.

• Symptoms include central obesity, hypertension, and skin changes.

Thyroid Hormone Disorders

Thyroid Gland Hormones

• Secretes T4, T3, and calcitonin and is regulated by the hypothalamus-pituitary-thyroid axis.

Hypothyroidism

• Caused by autoimmune conditions (e.g., Hashimoto’s) and iodine deficiency.

• Symptoms: fatigue, cold intolerance, weight gain, and goiter.

• Clinical tests indicate elevated TSH with low T4 levels.

Hyperthyroidism

• Results from excess hormone production, often due to Graves’ disease.

• Symptoms include weight loss, heat intolerance, palpitations, and exophthalmos.

Diagnostic Tests for Thyroid Function

Key Tests

• Serum Thyroid Hormones (Free T4 and Total T3)

• Serum TSH

• Serum Thyroglobulin (as a tumor marker)

• Imaging tests like radioactive iodine uptake.

Dynamic Function Testing (DFT)

• Used to diagnose endocrine disorders by stimulating or suppressing hormonal responses.

Types of Dynamic Function Tests

• Insulin Stress Test: Investigates GH and ACTH secretion.

• Oral Glucose Tolerance Test: Evaluates GH responses.

• TRH Stimulation Test: Assesses TSH responsiveness.

• ACTH and Dexamethasone Suppression Tests: Investigate adrenal hypofunction and Cushing’s syndrome.

Expected Results and Procedures of DFTs

• Insulin Stress Test measures ACTH and cortisol after hypoglycemic induction.

• Oral Glucose Tolerance Test measures GH suppression post-glucose intake.

• ACTH stimulation tests assess adrenal gland response to synthetic ACTH.