Tutorial 6 Endocrine Disorders Flashcards
1
Q
Define a feedback system and explain why endocrine feedback mechanisms are so important for maintaining homeostasis
A
- Feedback system can consist of a negative or positive feedback loop
- Most are negative feedback loops
- Feedback systems allow for the required levels of hormones to be maintained so as not to result in disease/imbalance.
2
Q
Define a negative feedback (blood glucose regulation)
A
- Stimulus: Rising BGL e.g. after eating
a. Beta cells of pancreas stimulated to release insulin into the blood
b. Insulin stimulates:
- body cells take up more glucose
- liver takes up and stores it as glycogen
c. Blood glucose level declined to a set point; stimulus for insulin release diminishes - Stimulus: Falling BGL e.g. skipping a meal
a. Alpha cells of pancreas stimulated to release glucagon into the blood
b. Glucagon stimulates:
- liver releases glycogen and releases glucose into the blood
c. BGL rises to set point; stimulus for glucagon release diminishes
3
Q
Define a positive feedback loop (oxytocin in childbirth)
A
- The baby pushes against the cervix, causing it to stretch
- The stretch of cervix causes nerve impulses to be sent to the brain
- The brain stimulates the pituitary to release oxytocin
- Oxytocin causes the uterus to contract to push the baby out
4
Q
State the common pathophysiological mechanisms of endocrine disorders
A
Three groups:
1. Endocrine hypersecretion - excess hormone production
- Endocrine hyposecretion - hormone insufficiency
- Tumours of the endocrine glands
5
Q
Describe the common hypothalamic-pituitary disorders and the main hormones involved
A
- Hyperpituitarism or hypopituitarism
- Acromegaly (pituitary) - excessive growth hormone
- Prolactin secreting tumours
- Diabetes insipidus due to ADH secretion
- Syndrome of inappropriate ADH secretion
- Hypothalamic disease may cause deficiencies in any downstream hormone e.g. TSH (thyroid-stimulating hormone), adrenocorticotrophic hormone, beta-endorphin, luteinizing hormone, FSH, MSH
6
Q
Describe two main thyroid and parathyroid disorders and discuss the main hormones involved
A
- Graves disease (toxic diffuse goitre) - hyperthyroidism
An autoimmune disorder where thyroid-stimulating immunoglobulins bind to the thyroid cells and stimulate the production of too much thyroid hormone - Hashimoto’s disease
Autoimmune thyroiditis - inflammation damages the gland leading to decreased thyroid production - Hyperparathyroidism
excess PTH and too much calcium in the blood - Hypoparathyroidism
not enough PTH and low calcium in the blood
7
Q
Describe 2 main adrenal gland disorders including symptoms and causes and discuss the main hormones involved
A
- Cushing’s syndrome - too much cortisol
a. Symptoms include: rapid weight gain (central obesity), buffalo hump, moon face, hirsutism, baldness, depression and anxiety
b. Causes: May be from exogenous administration of glucocorticoids or endogenous pituitary adenoma, adrenal tumours, paraneoplastic Cushing’s common from small cell lung cancer. - Addison’s disease - too little cortisol
a. Symptoms include: chronic fatigue, muscle weakness, weight loss, loss of appetite sometimes, N&V, fainting and low BP
b. Causes: adrenal insufficiency, secondary adrenal insufficiency caused by ACTH deficiency e.g. removal of the pituitary, tuberculosis which can destroy the adrenal glands, cancer and chronic fungal infection
8
Q
Define diabetes mellitus, and explain how it differs from diabetes insipidus?
A
- Patient with both types will feel thirsty and urinate frequently
- DM is caused by a lack of insulin or insulin resistance whereas diabetes insipidus is caused by a lack of hormone vasopressin (ADH)
- Diabetes insipidus is uncommon
9
Q
Define metabolic syndrome
A
- Combination of conditions that increase the risk of cardiovascular disease
- Diagnostic criteria include 3 or more of the following:
a. abdominal obesity (waist circumference)
b. elevated triglyceride
c. HTN
d. glucose intolerance/insulin resistance
e. Decreased HDL cholesterol
10
Q
State 3 common complications of diabetes mellitus and describe the pathophysiological causes?
A
- Heart and blood vessel disease:
excess glucose binds to the blood vessel wall causing thickening and hardening to occur. - Neuropathy (nerve damage):
excess glucose can damage the capillaries that nourish the nerves - Nephropathy:
damage to the nephrons - Retinopathy (eye damage):
blood vessels at the back of the eye balloon into pouches, this can ultimately lead to bleeding and loss of vision - Osteoporosis:
Diabetes can decrease your bone mineral density and increase your risk of osteoporosis - Hearing impairment
- Alzheimer’s disease:
Caused by blocking blood blow to the brain or by increased insulin causing brain-damaging inflammation
11
Q
Describe the risk factors/causes, pathophysiology and clinical manifestation of Inappropriate Anti-diuretic Hormone Secretion
A
- Causes: head injury, pituitary surgery, pulmonary diseases and lung tumours etc.
- Pathophysiology:
a. increased ADH (antidiuretic) or vasopressin, causing inability to excrete dilute urine
b. retention of free water
c. expansion of extracellular volume
d. dilutional hyponatremia - Clinical manifestation:
oliguria, weight gain, anorexia, N&V, muscle weakness, seizures, coma
12
Q
Describe the pathophysiology of T2DM
A
- Genetic and environmental factors:
increased appetite, nutrient intake, metabolic sufficiency - Physiological changes:
a. increased adiposity:
low grade inflammation, reactive oxygen species, dyslipidemia, adipokines, beta cell stress
b. Insulin resistance: liver and muscle
c. beta cell dysfunction - Excess glucose production, impaired glucose uptake and utilisation lead to T2DM
13
Q
How do we diagnose an alteration in endocrine function?
A
- Signs and symptoms: coma, oedema
- Blood tests:
a. BGL for diabetes
b. T3, T4 tests for thyroid function
c. other elevated hormone levels - Diagnostic imaging of the endocrine organ
e. g. MRI, CT
