Endocrine Physiology Flashcards
Cortisol (steroid hormone) is derived from which precursor?
Cholesterol - pregnenolone - progesterone - 17-OH-progesterone - 11-deoxycortisol - cortisol
Which enzyme catalyzes the conversion of 17-OH-progesterone to 11-deoxycortisol?
21-hydroxylase
The majority of cortisol is bound to which transport protein within systemic circulation?
Corticosteroid Binding Globulin / transcortin (75%)
Albumin (15%)
Free fraction 10%
Which factor(s) stimulate the release of cortisol
ACRH released from anterior pituitary Circadian rhythm Stress Trauma Burns Infection Exercise Hypoglycemia
Cortisol apposes the action of insulin.
What are the effects of cortisol on
- Skeletal muscle
- Adipose tissue
- Liver
- Cardiovascular system
- Immune system
- Protein catabolism - increases production and uptake of amino acids
- Lipolysis - increases production and uptake of free fatty acids and glycerol
- Gluconeogenesis, glycogenesis
1.4.
Increases the blood vessels sensitivity to epinephrine - vasoconstriction
1.5.
Anti-inflammatory action
Immunosuppressive effects
Which factor(s) stimulate the release of aldosterone?
- Renin-angiotensin-aldostrone system - activated by - - - decrease ECF volume
- Increase [K] in plasma
ACTH does not play a role
List the actions of aldosterone
Stimulate reabsorption of Na from DCT
Secretion of K into DCT
Secretion of H into DCT
Aldosterone is derived from which precursor?
Cholesterol - pregnenolone - progesterone - 11-deoxycorticosterone - corticosterone - aldosterone
The adrenal medulla is made up of neural tissue namely ______ cells?
Chrommafin cells (intramural ganglion)
What is the precursor for norepinephrine (precursor for epinephrine)?
Tyrosine - L-dope - dopamine - norepinephrine (20%) - epinephrine (80%)
Within the chromaffin cell
What are the effects of epinephrine on various physiological processes?
Stimulates glycogenolysis - B2 Stimulates glucagon - B2 Stimulates lipolysis - B3 Stimulates insulin secretion - B2 Stimulates K uptake by muscle - B2 Increases HR - B1 Increases arteriolar tone in skeletal muscle - B1 Increases cardiac contractility - B1 Bronchodilatation - B2
What are the effects of norepinephrine on various physiological processes?
Stimulates gluconeogenesis - A1 Inhibits insulin secretion - A2 Vasoconstriction - increase BP - A1 Increase tone in GI sphincters - A1 Bronchoconstriction - A1
Addison’s disease is caused by destruction of the adrenal cortex.
What are the clinical features?
Clinical features are mainly due to mineralocorticoid and glucorticoid deficiency
Aldosterone: Hypotension Hyponatreamia (due to decreased reabsorption) Hyperkalaemia Metabolic acidosis
Cortisol: Weight loss Anorexia Lethargy Hypoglycaemia Reduced resistance to trauma and infection
Hyperaldosteronism may be primary or secondary
- List the causes of each
- Clinical features
1.1.
Primary - adrenal adenomas 60-70% (Conn’s syndrome); bilateral hyperplasia
Secondary - increased secretion of renin by the JG cells - RAS, CCF, cirrhosis
1.2. Hypertension Hypernatraemia Hypokalaemia Metabolic alkalosis
Which factor(s) stimulate the release of growth hormone?
Hypoglycaemia (potent stimulator) Pain Anxiety Exercise Fever Trauma Hemorrhage
Pheochromocytoma is a tumour of the chromaffin cells of the adrenal medulla.
- List the causes
- Clinical features
1.1. Rule of 10s
10% Malignancy
10% bilateral
10% extra-adrenal
1.4. Heart palpitations Tremors Sweating and flushing Increased BP (episode) Hyperglycemia (episodic)
PTH and Vitamin D increase plasma concentration of Calcium - describe their action
PTH -
Stimulates Calcium release from bone by stimulating osteoclast activity
Increases calcium uptake from renal tubules
Stimulates urinary phosphate excretion
Stimulates rate at which Vit D converted to biologically active form
Vit D -
Increases rate of Calcium and Phosphate uptake from gut
Increases renal tubular absorption of Calcium and phosphate
Stimulates osteoclastic bone resorption
Promotes mineralization of osteoid
Calcitonin is released from parafollicur C cells within the thyroid in response to high calcium plasma concentrations - describe it’s action
Decreases calcium and phosphate reabsorption from renal tubules
Stimulates osteoblasts to mineralize bone
The conversation of Vit D into it’s biologically active form is stimulated by _______?
PTH
Low plasma phosphate levels
List the differences between secondary and tertiary hyperpararhyroidism
- Cause
- Physiological effects
1.1.
Secondary - prolonged decreased levels of calcium - chronic renal failure
Tertiary - cause for secondary hyperpararhyroidism is not addressed
1.2.
Secondary -
Low-normal calcium level, elevated PTH
Tertiary
Elevated calcium and PTH levels
Insulin is an anabolic hormone released from the B-cells of the islet of Langerhans.
It is released in response to high glucose plasma concentration levels.
List it’s actions
Carbohydrate metabolism
- Promotes glycogenesis
- Decreases glycogenolysis
- Stimulates glycolysis (liver)
Protein metabolism
- Stimulates amino acid uptake and protein synthesis
- Inhibits protein degradation
- Inhibits amino acid convertion to glucose
Lipid metabolism
- Inhibits lipolysis by lipase
- Stimulates lipogenesis
Glucagon is released by the A-cells of the islet of Langerhans in response to low plasma concentration of glucose.
List it’s actions
Carbohydrate metabolism
- Stimulate glycogenolysis
- Stimulate gluconeogenesis
- Glucose sparing via preferential oxidation of FFA
Lipid metabolism
- Stimulates lipolysis
The secretion of somatostatin is stimulated by increase in plasma glucose and which other factors?
Increase in amino acids
Increase in plasma glycerol
Pancreatic endocrine tunours can result in various clinical syndromes when they are ‘functioning’ and secrete excess hormone.
Describe the clinical picture of an insulinoma
Whipple’s triad
Hypoglycaemia during fasting
Reduced blood glucose levels during these periods
Relief with IV glucose
Pancreatic endocrine tunours can result in various clinical syndromes when they are ‘functioning’ and secrete excess hormone.
Describe the clinical picture of an Gastrinoma (Zollinger-Ellison Syndrome)
Arise from pancreatic G-cells
Gastric hypersecretion
Diarrhoea
Widespread peptic ulceration
Pancreatic endocrine tunours can result in various clinical syndromes when they are ‘functioning’ and secrete excess hormone.
Describe the clinical picture of an Vipoma
Associated with excess secretion of VIP (vasoactive intestinal peptide)
Severe watery diarrhoea
Hypokalaemia
Achlorydria (abscence of HCl in stomach)
Pancreatic endocrine tunours can result in various clinical syndromes when they are ‘functioning’ and secrete excess hormone.
Describe the clinical picture of an glucagonoma
Rare secondary cause of diabetes mellitus
Anaemia
Weight loss
Necrolytic migratory erythema (characteristic)
Multiple Endocrine Neoplasia (MEN) syndrome
Describe the conditions characterizing
- MEN 1
- MEN 2A
- MEN 2B
1.1. MEN 1
Pituitary adenoma
Pancreatic endocrine tumour
Parathyroid neoplasia
1.2. MEN 2A
Medullary thyroid cancer
Pheochromocytoma
Parathyroid hyperplasia or adenoma
1.3. MEN 2B Medullary thyroid cancer Pheochromocytoma Mucosal and gut Neuromas Marfanoid features
