Endocrinology Basics (y1/2) Flashcards
Where do lipid soluble hormones bind?
receptors in cytoplasm or nucleus
Where do water soluble hormones bind?
Receptors on cell surface
Where are the exocrine cells of the pancreas located?
Acini (clusters)
Where are the endocrine cells of the panrcreas located?
Amongst the acini - islets of langerhans
What are the 4 cell types of the pancreatic islet and what do they each secrete?
Alpha - glucagon
Beta - insulin
Delta - somatostatin
F cell - pancreatic polypeptide
What are the 3 targets of insulin?
Liver
Muscle
Adipose Tissue
Which 3 organs are NOT insulin dependent?
Brain (although NEEDS glucose)
Kidney
Intestine
What action does glucose have at a molecular level?
Inserts GLUT 4 transporters into cell wall.
What action does glucose have at a cellular level?
inc glucose metabolism
inc glycogen, protein and triglyceride synthesis
What action does glucose have at a tissue level?
decrease plasma glucose by:
inc transport into cells
OR
inc metabolic use
Apart from inc blood glucose, what 3 things may increase insulin secretion?
Inc plasma AA’s
Anticipatory release of GI hormones
Inc Parasympathetic activity during/post meal
What is the role of glucagon at a tissue level?
Glycogenolysis and Gluconeogenesis
Ketogenesis
Which tissue is the target of glucagon?
Liver
What is glucagon released in response to?
Dec plasma glucose
Inc plasma AA’s
Parasympathetic & SYMP (stress) activity
What is the role of somatostatin?
Decrease Growth Hormone
Stop insulin/glucagon release
What is the role of Pancreatic Polypeptide?
Unknown! increases after meals
What is Type 1 DM?
Inadequate insulin secretion
What is Type 2 DM?
Abnormal target cell response to insulin
What are the signs of DM?
Hyperglycaemia
Weight loss - low protein synth and low glucose cause muscle breakdown
PU/PD
ketoacidosis
What does the pituitary consist of?
2 fused glands:
AP: endocrine
PP: neural extension
What is secreted by the Posterior Pituitary?
Oxytocin
ADH
Where are ADH and oxytocin produced?
Hypothalamus
How do the hypothalamic hormones reach the AP?
Portal Capillary System
How do the hypothalamic hormones reach the PP?
In vesicles down neuron cell body
What are the 6 hormones secreted by the AP?
FLAT PiG:
FSH LH ACTH TSH Prolactin GH
What are the 3 releasing hormones that affect the AP?
TRH
CRH
GnRH
Where is thyroid hormone produced?
Thryoid Gland:
Follicular cells and T3/T4 assembled in colloid
How long does the supply of T3/T4 last in the thyroid?
2-3m
What is the main hormonal product of the thyroid gland?
T4
Which thyroid hormone is the most biologically active?
T3
Where is T3 produced?
Thyroid Gland
AND converted from T4 in peripheral tissues?
What is the role of the thyroid hormones?
Increase BMR Enhanced CHO utilisation Growth & development CV stimulant Promotes milk production
On which two organs does negative feedback from the thyroid occur?
AP
Hypothalamus
What are the 4 major signs of hyperthyroidism?
inc appetite and WL
Hyperthermia
Inc HR
Excitable
What are the 5 major signs of hypothyroidism?
Weight gain but no inc appetite Hypothermia Lethargy/Poor exercise tolerance Dec HR Dullness
Where is the adrenal gland in relation to the kidney?
Craniomedially
What are the 4 layers of the adrenal gland and what do they produce?
Cortex:
Zona glomerulosa: mineralocorticoid
Zona fasiculata: glucocorticoid
Zona Reticularis: androgens
Medulla: Adrenaline/Noradrenaline
What is the role of cortisol?
Liver: gluconeogenesis Other tissues: dec glucose uptake Adipose: Lipolysis Muscle: breakdown Immune: suppression
How do glucocorticoids aid vasoconstriction?
MUST be present for catecholamines to have vasoconstrictive effect
Which hormone stimulates the production of cortisol and sex steroids?
ACTH
What are the 3 causes of HAC?
Pituitary Dep HAC
Adrenal Dep HAC
Iatrogenic HAC
What are the clinical signs of HAC?
hyperglycaemia PUPD Tissue wastage Muscle weakness Pot Belly Hyperpigmentation
what is the role of mienralocorticoids?
regulate Na+/K+ in the blood i.e. aldosterone
What are the two major regulators of aldosterone?
Ang II and K+
What two factors induce the release of catecholamines?
Stress
Hypoglycaemia
What are the 4 major funcitons of catecholamines?
Inc CO
Blood –> skeletal muscle
Inc plasma glucose conc
Inc triglyceride breakdown
What is the target of GH and what is the effect?
Liver - IGF-1 production
What are the 3 effects of GH release?
Protein synthesis
Lipolysis
Inhibit glucose uptake
What increases GH secretion? (4 S’s)
CNS input
Strenuous physical activity
Starvation/dec plasma glucose
Stress
What is the pathway for the release of GH?
GHRH & somatostatin from hypothalamus –> GH from AP
What is acromegaly caused by?
Chronic excess of GH
What are the clincial fetaures of acromegaly and why?
Insulin resistant DM
Excessive extremity growth
Prognathism
Wide interdental space
Where is melatonin secreted from?
Pineal gland
What does melatonin control?
Circadian Rhythms
When is melatonin secretion increased?
In the dark - causes drowsiness and lower temp
Where is ANP secreted from and why?
Atrial Cardiac Myocytes due to inc BV/atrial stretch
What is the role of ANP?
Counter RAAS - dec BV
What is the role of leptin?
Inhibits appetite centre in hypothalamus
GLUT 2 is always present on hepatocytes. True or False?
TRUE - glucose can always pass in or out of hepatocytes. Insulin aids this by adding GLUT4.
Which insulin is good for acute ketoacidosis, but not regular use?
Crystalline Zinc
What is the advantage of lente insulin?
very long DOA (8-24h) but 30m onset
How does protamine zinc insulin have such a long DOA?
Protamine forms zinc crystals which slow insulin absorption
How should an insulin overdose be treated?
Feed
Give IV glucose
How does Metformin help in diabetes?
dec gluc abs from GIT
dec gluc output from liver
inc insulin receptor sensitivity
How does Glipizide help in diabetes?
stimulates insulin secretion by preventing K+ exiting cell
How can we treat an insulinoma medically?
Diazoxide - inhibits insulin secretion by activating K+ and inhibiting Ca in beta cell
Why are ketone bodies produced in diabetes?
High glucose in plasma but cant enter cells where it is needed!!
Where is TRH produced?
hypothalamus
Where is TSH produced?
anterior pituitary
Where is T3/T4 produced?
thyroid gland
What is the most definitive test for hypothyroidism?
TSH stimulation: - Basal T4 - Inject TSH - Repeat T4 NORMAL: increase by >1.5x
Name 2 thyroid hormone replacement therapies?
Levothyroxine (T4)
Liothyroxine (T3)
Which animal has they greater T4 half life; Cats or Dogs? Why?
Dogs - increased levels of TBG. More hormone bound in plasma so cannot activate receptors.
What test would you perform on a suspected hyperthyroid cat?
tT4 - if low end of ref interval, use fT4 too
What is the T3 suppression test?
Basal tT4
Oral T3 for 3d
Normal: 50% suppression
Name 3 treatments for hyperthyroidism in cats.
Methimazole
Carbimazole
Radioactive iodide
Why treatment for feline hyperthyroidism requires hospitalisation for 1-4w?
Radioactive Iodide
What are changes on a stress leucogram?
Segmented Neutrophilia
Monocytosis
Lymphocytopenia
Eosinopenia
What are the 2 causes of HyperAC and what changes can you see on bloodwork for each?
Functioning Adrenal Tumour (inc cortisol, dec ACTH)
Functioning Pituitary Tumour (inc cortisol, inc ACTH)
What are the signs of a primary hypoadrenocorticism?
Acute Hypovolaemic shock
Bradycardia (^K+)
What are the 2 causes of HypoAC and what changes can you see on bloodwork for each?
Primary (dec cortisol, inc ACTH)
Secondary (dec cortisol, dec ACTH)
What are the two tests for adrenocortical Dz?
ACTH Stim
Dex ST
Name 2 SHORT acting glucocorticoids.
Hydrocortisone
Cortisone
Name 3 intermediate acting glucocorticoids.
Prednisone
Prednisolone
Methylpred
Name 2 LONG acting glucocorticoids.
Betamethasone
Dexmethasone
Name 2 drugs commonly used to treat PDH orADH.
Trilostane - inhibits c/s synthesis
Mitotane - cytotoxic to ZF & ZR
Which adrenal steroid inhibitor should NOT be used in pregnant animals, and why?
Trilostane - inhibits progesterone synthesis
What is the main role of PTH?
Prevent hypocalcaemia - dec Ca in ECF stimulates secretion
What is the main role of Calcitonin?
Prevent hypercalcaemia - inc Ca in ECF stimulates secretion
What are the 3 main targets of PTH?
Bone
Intestine
Kidneys
What is the main target of calcitonin?
Bone
What are 3 ECG signs that IV Ca administration should be stopped?
Elevated ST segment
Short QT intervals
Arrhythmias
State the 2 anti-diuretic drugs used to treat DI and state which is better and why.
Vasopressin
Desmopressin: better as less vasoconstriction and longer DOA