Non-endocrine gland endocrinology Flashcards
What are the incretins?
Gastric-inhibitory peptide (GIP)
Glucagon like peptide (GLP-1)
Where is gastrin produced from?
G cells in duodenum and stomach
What is the stimuli that causes gastrin secretion?
Presence of peptides and AAs in gastric lumen
Stomach distension
Vagal stimulation
Hypercalcaemia
What are the major effects of gastrin?
Stimulates release of gastric acid from parietal call - decreased pH
Stimulates release of pepsinogen from chief cells
Why is gastric secretion inhibited at ~pH3
Further decrease in pH can cause gastric ulceration
What is the clinical relevance of gastrin in cats and dogs
Gastrinomas - tumours in gastric secreting cells
Leads to excessive gastrin production => vomiting, inappetance, abdominal pain
Where is secretin produced?
duodenum
What stimuli causes secretin secretion?
H+ in SI/acid from stomach
What is the major effect of secretin?
Stimulates release of bicarbonate-rich pancreatic and biliary fluid to buffer gastric acid
Where is cholecystokinin (CKK) produced?
duodenum
Brain cells
What is the stimuli for CCK (cholecystokinin) release?
fatty acids, monoglycerides and AAs in SI
Expansion of stomach after meal => CCK in brain
Where is gastric inhibitory polypeptide (GIP) produced?
Proximal SI
What is the stimuli that causes the secretion of GIP (gastric inhibitory polypeptide)?
Fat, glucose and AAs in SI
What are the major effects of GIP (gastric inhibitory polypeptide)?
Inhibits gastric secretion and motility
Increases release of insulin in response to elevated blood glucose levels
Increases insulin sensitivity of adipocytes
Stimulation of lipoprotein lipase activity in adipocytes
Where is GLP-1 (glucagon like peptide) produced?
L-cells of ileum and jejunum
What stimulates GLP-1 (glucagon like peptide) secretion?
CHO, fat and protein in SI
What is the effect of GLP-1 (glucagon like peptide)
Promotes insulin secretion
Suppresses glucagon driven gluconeogenesis
Slows gastric emptying
Promotes satiety/fullness in hypothalamus
Where is Ghrelin produced?
Stomach
What stimulus causes ghrelin secretion?
starvation
What is the action of ghrelin?
strong stimulant for appetite and feeding
Which nuclei of the hypothalamus is responsible for appetite regulation?
arcuate nucleus
What hormones control appetite?
Leptin causes satiety (anorexigenic)
Ghrelin stimulates appetite (orexigenic)
What is the action of the satiety and appetite centres in the hypothalamus?
Satiety centre:
- respond to high glucose levels
- inhibits eating
Appetite centre:
- responds to low glucose levels
- stimulates eating
How do ghrelin and leptin regulate appetite?
Insulin and leptin interact with POMC in arcuate nucleus of hypothalamus to inhibit appetite
Ghrelin inhibits insulin and leptin
What are the effects of having no leptin production/response?
hyperphagic - always hungry => obesity
Hypothermic
Infertile
What is the effect of CCK
Released rapidly in response to a meal:
- stimulates gallbladder contraction
- secretion of pancreatic enzymes and bicarbonate
- slows gastric emptying
- inhibits gastric acid secretion
- reduces food intake
What are the most relevant adipose hormones?
Leptin
Adinopectin
What is action of adinopectin?
improves insulin sensitivity
low in obesity and insulin resistant states
What are the renal hormones?
Erythropoietin
Renin
Calcitriol
What is the source, stimuli and function of erythropoietin
Produced by interstitial fibroblasts of kidney
Response of hypoxia
Promotes RBC production
What is the source, stimuli and action of renin?
Produced by juxtaglomerular cells of kidney
Respond to decreased arterial pressure
Initiate RAAs to improve/increase blood pressure and volume
Describe the renin-angiotensin aldosterone system
what are the heart hormones/natriuretic peptides
BNP
ANP
What is the source of BNP?
ventricular cardiomyocytes
What is the stimuli for BNP secretion?
stretch of ventricles caused by increased blood volume
What is the action of BNP?
reduced vascular resistance (lower BP)
Affects afferent and efferent glomerular arterioles to increase hydrostatic pressure and promote GFR
Weakens medullary conc gradient (promote water loss)
Promotes Na loss from kidney
Reduces aldosterone production
what is Zollinger-ellison syndrome and what are the clinical consequences?
Excess gastrin
Clinical consequences:
- chronic gastric ulcers due to excess gastric acid
- vomiting due to stomach acidity
- diarrhoea - acid secretion irritates intestines
- Weight loss
- dehydration
- abdominal pain
- inappetance
- Haematemsis (vomiting blood)
