Chapter 9 Selected Diseases and Disorders of the Endocrine System
9.1e Endocrine Homeostasis and Dysfunction
Zoë Soon
Main Functions of Key Hormones
- Proper hormone levels are vital; underproduction or insensitivity results in dysfunction.
- Excess production can cause tissue damage or abnormal growth.
Common Endocrine Disorders Overview
- Growth hormone deficiency: Causes less growth in childhood.
- Excess growth hormone: Causes excessive height or acromegaly.
- ADH deficiency: Known as diabetes insipidus:
- Causes excess urination (polyuria).
- Leads to dehydration and thirst.
- Excess ADH: Causes SIADH:
- Leads to water retention, weight gain, and possible edema.
- Thyroid hormone imbalance:
- Hypothyroidism: Slows metabolic processes, causes cold intolerance, developmental delays.
- Hyperthyroidism: Speeds up metabolism, causes heat intolerance, weight loss, Graves’ disease.
- Parathyroid hormone imbalance:
- Hypoparathyroidism: Bones become overly dense, neurological issues.
- Hyperparathyroidism: Bones weaken and become brittle, neurological issues.
Type I Diabetes Mellitus (Insulin Deficiency)
- Type 1: Autoimmune destruction of pancreatic beta cells.
- Results in insufficient insulin production.
- Without insulin cells of the body are unable to insert GLUT4 glucose transporters into their cell membranes to allow for glucose uptake by cells.
- Causes high blood glucose levels
- Causes lipolysis which increases blood lipid levels
- Causes gluconeogenesis and glycogenolysis which increases blood glucose levels
- Causes glucosuria, polyuria, dehydration, polydipsia, and polyphagia
- Can cause ketoacidosis and electrolyte imbalances
- Causes high blood glucose levels, which are toxic to blood vessel walls.
- Affects all cells requiring glucose
Type II Diabetes Mellitus (Insulin Insensitivity / Resistance)
- Type II: Insulin insensitivity, leads to cells being less responsive to insulin and unable to insert GLUT4 glucose transporters into their cell membranes to allow for glucose uptake by cells.
- Causes high blood glucose levels
- Causes lipolysis which increases blood lipid levels
- Causes gluconeogenesis and glycogenolysis which increases blood glucose levels
- Causes glucosuria, polyuria, dehydration, polydipsia, and polyphagia
Excess Insulin Production
Rare, but results in low blood glucose levels, risking hypoglycemia and brain dysfunction.
Summary
- Endocrine disorders often result from hormone underproduction or target tissue insensitivity.
- Recognizing symptoms helps in diagnosing and treating these issues through hormone supplements or blockers.
- Maintaining hormone balance is crucial for health and proper physiological functioning.
This table illustrates the clinical implications of endocrine dysfunction.
| Hormone | Underproduction of Hormone or Tissue Insensitivity to Hormone | Signs and Symptoms | Overproduction of Hormone or Hypersensitivity to Hormone | Signs and Symptoms |
| Growth Hormone (GH) | Pituitary gland growth failure | Delayed growth; Abnormal fat distribution; Low blood glucose hours after a meal | Gigantism (if GH overproduction occurs during childhood);
Acromegaly (if GH overproduction occurs during adulthood) |
Excessive growth in height during childhood;
Excessive thickness of bone during adulthood |
| Antidiuretic (ADH) | Diabetes insipidus | Polyuria, dehydration, thirst | SIADH (Syndrome of Inappropriate ADH secretion) | Increased body weight and water content |
| Thyroxine (T4) Triiodothyronine (T3) | Hypothyroidism;
Infantile hypothyroidism; Myxedema |
Low metabolic rate; Low body temperature; Impaired physical & mental development | Hyperthyroidism;
Graves Disease |
High metabolic Rate; High body temperature |
| Parathyroid Hormone | Hypoparathyroidism | Muscular weakness;
Neurological problems; Formation of dense bones and tetany due to low blood Ca2+ levels (because osteoclast activity it too low!) |
Hyperparathyroidism | Neurologic, mental, muscular problems due to high blood Ca2+ levels and weak and brittle bones (because osteoclast activity it too high!) |
| Insulin | Type 1 Diabetes Mellitus (autoimmune disease) | High blood glucose, high blood lipid levels, increased lipolysis in adipose cells, increased glycogenolysis, increased gluconeogenesis, glycosuria, ketonemia, polyuria, polyphagia, polydipsia | Excess insulin production or administration | Low blood glucose levels, possibly causing coma |
