Endo pre-clinical

Question 1

In the management of vitamin D deficiency, how does cholecalciferol work?

Answer 1

• Increases intestinal absorption of both calcium & phosphate
• Enhances calcium & phosphate reabsorption in the kidneys
• Helps mobilise these minerals from bone when needed

Question 2

Why can antipsychotics (eg. risperidone) cause galactorrhoea?

Answer 2

• They inhibit dopamine –> reducing dopamine-mediated inhibition of prolactin

(prolactin stimulates the mammary glands to produce milk)

Question 3

Other than activation of the RAAS system, ADH release is another mechanism to retain water and increase BV and therefore BP, how does ADH work?

Answer 3

increases insertion of AQP-2 channels in the collecting duct to increase water reabsorption

Question 4

What physiological effects does increased cortisol have?

Answer 4

1. Increases gluconeogenesis
2. Dampens immune system
3. Up-regulation of alpha-1-adrenoreceptors on arterioles –> high BP as smooth muscle is more sensitive to the circulating norepinephrine & epinephrine
4. Decreases osteoblast activity –> therefore high cortisol lvls can reduce the formation of new bone and result in weak bones
5. Decreases fibroblast activity & collagen synthesis –> therefore high lvls can result in delayed wound healing
   (abdominal stria is usually due to decreased college synthesis)

Question 5

PTH is released by the chief cells of the parathyroid glands.

How does PTH work on the:
- bone
- kidney
- intestine via kidney

Answer 5

• Bone: binds to osteoblasts which signal to osteoclasts to cause resorption of bone & release calcium
• Kidney: active reabsoprtion of calcium & magnesium from the distal convoluted tubule (decreases reabsorption of phosphate)
• Intestine via kidney: increases intestinal calcium absorption by increasing activated vitamin D
  (activated vitamin D increases calcium absorption)

Question 6

How do DPP-4 inhibitors (eg. sitagliptin) work to reduce blood sugar levels?

Answer 6

• Increases lvls of incretins (ie. GLP-1) by decreasing their peripheral breakdown
• Increased incretin lvls then work to decrease blood glucose lvls

Question 7

What is the MOA of carbimazole & propylthiouracil (PTU)?

Answer 7

• Carbimazole: blocks thyroid peroxidase from coupling & iodinating the tyrosine residues on thyroglobulin –> reducing thyroid hormone production
• Propylthiouracil: as well as this central MOA, also has a peripheral action by inhibiting 5’-deiodinase which reduces peripheral conversion of T4 to T3

Question 8

Explain how alcohol causes hyperglycaemia initially & then hypoglycaemia later on (ie. during the night after an alcohol binge).

Answer 8

• the carbohydrates in alcoholic drinks can cause blood glucose to rise
• this is then followed by the alcohol inhibiting glycogenolysis and so causing a late hypoglycaemia (ie. during the night)