Repro & Endocrine Flashcards
The penile urethra sits within which muscle?
Corpus spongiosum
What is the name of the plexus taking away blood from the testes?
Pampiniform plexus
Where is each lobe of the pancreas located in the dog?
Right=within meso-duodenum
Left=within deep leaf of greater omentum
Which cells exist within islets of Langerhans in the pancreas?
Alpha and beta cells
How are exocrine cells arranged in the pancreas?
What about endocrine cells?
Exocrine=clusters called acini
Endocrine=islets of Langerhans
In the pancreas, what do acini produce?
Digestive enzymes that flow through ducts into the GI tract
Give 3 other catabolic hormones besides glucagon
Cortisol
Growth hormone
Catecholamines
What is the difference between type 1 and type 2 diabetes?
Type 1=inadequate insulin secretion
Type 2=abnormal target cell responsiveness
How does glucose enter cells?
Is this an active or passive process?
Through GLUT transporters
Passive (concentration gradient)
How does insulin increase glucose uptake in skeletal muscle, adipocytes and other cells?
Signals the cell to inset GLUT4 transporters into the membrane, allowing glucose to enter
What are the 3 things glucose can be converted to?
Glucose-6-phosphate
Glycogen
Fat
How is glucose taken up into hepatocytes?
Glucose enters the cell using GLUT2 transporters.
Insulin stimulates hexokinase to maintain a low intracellular concentration of glucose (converts glucose to glucose 6-phosphate)
What is the difference between presence of transporters in the membranes of hepatocytes compared with skeletal muscle, adipocytes and other cells?
Hepatocytes: GLUT2 transporters are ALWAYS present in the cell membrane (not insulin-dependant), transport in both directions.
Skeletal muscle cells: GLUT4 transporters are only present in the cell membrane when insulin signals the cell to insert them there. Only allow glucose to enter, not leave.
Are neurones sensitive to insulin?
No
How does excess glucose in the CSF affect neurones in the CNS?
Increases osmolarity of CSF, drawing water out of neurones
How does insulin decrease blood concentrations of glucose?
Increasing glycogen synthesis
Decreasing hepatic glycogenolysis
Decreasing gluconeogenesis
Increasing glucose transport into skeletal muscle cellls and adipocytes through GLUT4 transporters
What effect does insulin have on protein metabolism?
Increases protein synthesis and uptake of amino acids
What effect does insulin have on fat metabolism?
Increases fat synthesis and decreases lipolysis
What effect does insulin have on K+?
Increases uptake of K+ into skeletal muscle and fat cells by providing ATP to activate the NA+/K+ ATPase pump
Describe the structure of insulin and discuss species similarities
Insulin=2 peptides joined by a disulphide bridge.
Porcine and canine insulin molecules are identical, and only differ from human insulin by a single amino acid.
Feline and bovine insulin are similar in structure.
Water-soluble.
What kind of receptors does insulin bind to?
Tyrosine kinase membrane receptors
What is the plasma half-life of insulin?
What about biological half-life?
Plasma= 5-10 mins
Biological=several hours
In which species is the bulbourethral gland absent?
Dog
Sexual maturity is signalled by what?
Increased GnRH pulsatility
Where is insulin metabolised?
Liver and kidney
Which form of lente insulin has the longer duration?
Ultralente
What is the average duration of a soluble insulin formulation?
What about non-soluble?
Soluble=3-6 hours
Non-soluble=6-24 hours
What is meant by postprandial?
eg postprandial hyperglycaemia
After eating
Give 2 adverse effects of using exogenous insulin?
Hypoglycaemia Insulin resistance (due to stress, insulin antibodies, or insulin receptor desensitisation)
How may stress induce exogenous insulin resistance?
By increasing secretion of adrenaline and corticosteroids
What is an advantage of using an oral antihyperglycaemic over exogenous insulin?
Does not stimulate insulin secretion so does not cause hypoglycaemia
Which channels does glipizide (anti-diabetic agent) block?
ATP-sensitive potassium channels
Name a drug you could use to treat hyperinsulinism
How does it work?
Diazoxide
Activates potassium channels causing inhibition of voltage-gated Ca2+ channels
Inhibits insulin secretion
What is the hormone relaxin produced by?
What does it do?
Produced by ovary and placenta in preparation for parturition
Softens the broad ligament, pelvic ligaments and sacroiliac joint
Where is the thyroid located?
Two lobes located either side of the trachea just below the larynx
Where is thyroid stimulating hormone released from?
Anterior pituitary gland
Explain the thyroid hormone feedback loop
Thyroid stimulating hormone (TSH) is released by anterior pituitary in response to TRH secreted into the portal system from the hypothalamus. TSH causes the synthesis and secretion of T3 and T4 into the blood from follicular cells in thyroid. Elevated T3 inhibits release of TRH and TSH.
TSH also inhibits release of TRH from the hypothalamus
What are the 5 functions of thyroid hormones?
Increase BMR
Normal growth and development (T3 causes increased GH secretion, maintenance of nerve function, hair growth)
Cardiovascular stimulant (increased CO)
Enhances CHO utilisation and lipolysis (increases LDL uptake by liver)
Promotes milk production
Give some signs of hypothyroidism
Poor exercise tolerance Weight gain with no change in appetite Intolerance to cold and hypothermia Mental dullness Increased blood cholesterol Decreased heart rate Bilateral symmetrical alopecia
How much should T4 increase by after injecting TSH?
1.5 times
T3 is how many times as active as T4?
3-5
In thyroid hormone replacement therapy, what is used to replace:
T3
T4
T3= Liothyronine T4= Levothyroxine
Explain the metabolism of thyroid hormones
30-40% T4 is converted to T3 in peripheral tissues
50% T4 is converted to reverse t3 (inactive)
20% T4 and 100% T3 form conjugates of glucoronide and sulphur in liver and are excreted in bile
How are thyroid hormones transported and bound?
Transported bound to plasma proteins
Free protein binds to target receptors. Bound fraction provides a depot that lasts several days, as when free molecules bind to their target receptors, more molecules dissociate from bound protein.
What are the 4 sigs of hyperthyroidism?
Weight loss with increased appetite
Hyperthermia
Increased heart rate
Excitable
How can you test for hyperthyroidism?
Test for serum T4 levels (will be high)
Describe the T3 suppression test when testing for hyperthyroidism
Take basal TT4 (total T4).
Give oral T3 for 3 days.
Resting T4 should be suppressed by >50%.
If little/no suppression -> producing excess T4 from thyroid gland.
Which drugs can be used to treat hyperthyroidism?
Felimazole
Methimazole- inhibits synthesis of T3 and T4
Carbimazole (metabolised to methimazole)
What is an alternative to surgical thyroidectomy?
What considerations are there?
Radioactive iodine
Destroys radioactive follicles
Treated animals need to be hospitalised for 1-4 weeks
Treated animals and excrete need to be handled carefully until radioactivity is gone
What is a goitre?
What could cause it?
Enlarged thyroid gland
Could be due to tumour, or iodine deficiency
Explain how an iodine deficiency could lead to an enlarged thyroid gland and hyperthyroidism
Lack of iodine in diet (eg lack in soil-sheep)/ substances that inhibit uptake
Can’t make thyroid hormones. Continually high TSH stimulates thyroid follicular cell growth. No negative feedback
Enlarged thyroid
All steroid hormones from the adrenal cortex are formed from which molecule?
What is this then converted to?
Cholesterol
Pregnenalone
How are steroid hormones transported?
Bound to plasma proteins
Lipid-soluble
What is the mechanism of action of corticosteroids?
Act on intracellular receptors to alter mRNA synthesis
What type of corticosteroid is aldosterone?
Mineralocorticoid
What are the 3 normal functions of cortisol?
Increased blood glucose
Increased protein catabolism
Increased lipolysis
What are the clinical signs of hyperadrenocorticism?
Hyperglycaemia PU and secondary PD Tissue wasting Muscle weakness Pot belly Increased skin pigment (synthesis of ACTH involves a precursor: POMC which stimulates MSH -> increases melanin production)
What would you see on a stress leucogram?
Lymphocytopenia (decreased lymphocytes)
Monocytosis (increased monocytes)
Eosinopenia (decreased eosinophils)
Neutrophilia (increased neutrophils)
What is a stress leucogram caused by?
Stress response or corticosteroid induced
How you would distinguish a functioning adrenal tumour from pituitary-dependant hyperadrenocorticism?
Pituitary tumour- increased ACT
Adrenal tumour- decreased ACTH
Name a common mineralocorticoid drug
Fludrocortisone
What percentage of the body’s Ca2+ is found in bone?
What is it found as?
99%
Hydroxyapatite
What is PTH secretion controlled by?
Serum-ionised calcium
What are the effects of PTH?
Increases Ca2+ by affecting transport mechanisms in bone, kidney, and indirectly (via Vit D) the intestine
Increased absorption from GI tract
Increased osteoclastic activity so that Ca2+ is released from bone into blood
Increases renal excretion of phosphate
What does vitamin D3 do?
Enhances Ca2+ uptake from small intestine
Increases intestinal absorption of phosphate and decreases renal excretion
What does calcitonin do?
Where is it released from?
Decreases Ca2+, largely by affecting transport mechanisms in bone (less active bone remodelling by osteoclasts)
Comes from parafollicular cells of thyroid gland
Why might you not administer calcium IV?
Can cause cardiac arrhythmias and arrest
What is calcitriol?
Active vitamin D3
Vasopressin and desmopressin are examples of what?
What are they used to diagnose/treat?
Anti-diuretics
Used to diagnose and treat diabetes insipidus
What is somatotropin?
A growth hormone stimulant
What does cabergoline do?
What is it used for?
Stops lactation
Induces oestrus and abortion in bitches
Treats false pregnancy
What are the 6 hormones produced by the anterior pituitary gland?
FSH, LH, ACTH, TSH (thyroid stimulating hormone), GH and prolactin
What are the 2 types of receptor for sex-steroid hormones?
Nuclear receptors (slow) Membrane receptors (fast)
Name the commonly-used exogenous oestrogen
Oestradiol
