Endo Physiology Flashcards
How does calcitrol (vit d) alter instestinal absorption of calcium?
Increases intestinal absorption of calcium by increasing expression of luminal calcium channels, calcium binding proteins and extrusion proteins= more calcium being absorbed from the cells of intestinal mucosa
Synthesis of thyroid hormones depends especially on what?
Iodine availability
How is iodide transported from the bloodstream into follicular cells?
Na/I symporters located on basolateral membrane of follicular cells- a form of active transport
What does oxytocin do?
stimulates the release of breastmilk and contraction of uterus in childbirth
What does the adrenal cortex secrete
Corticosteroids eg aldosterone and cortisol
What does the adrenal medulla secrete
Catecholamines eg epinephrine and norephrine or adrenaline
What would insulin deficiency cause to GLUT channels
Low GLUT-4 expression and therefore uptake of insulin on cell surface and therefore more glucose to be circulating in the blood = hyperglycaemia
What electrolyte abnormalities are seen in primary hyperthyroidism- think systematically
- Tumour leading to excessive levels of PTH
- PTH stimulates kidneys to remove phosphate from blood
= hypophosphaemia
What does PTH do to blood calcium and by what mechanisms?
Raises blood calcium by:
1. increases osteoclast activity of bones by reabsorbing calcium from bones
2. Increase calcium reabsorption in the kidneys (DCT) so less lost in the urine
3. Increases Vit D activity so increased calcium absorption in the intestines
What happens when blood calcium levels are high
Calcitonin released from thyroid so blocks osteoclast activity
What is secondary hyperparathyroidism
Insufficient vit D or CKD causing reduced calcium absorption from intestines, kidneys and bones = hypocalcemia.
Parathyroid reacts by excreting more parathyroid hormone
Ca= Low, PTH= high
What are examples of catecholamines
Adrenaline
What disease would you measure free catecholamines
Phaecromocytoma
Why is Cushings associated with hypokalemia
Excess cortisol exhibits mineralocorticoid activity by binding to activating Na/K pumps causing potassium movement into cells
What is the typical half life of insulin
Less than 30 mins
How to DDP-4 inhibitors work?
Eg sitaglitpins
Inhibit enzyme responsible for breaking down incretin so leads to increased incretin levels in the blood this works to increase insulin levels
How do glucocorticoids work
Bind to intracellular receptor that migrates to the nucleus and affects gene transcription
What can corticosteroids worsen
Have anti-insulin effects so worsen diabetic control
Cortisol is an example of a
glucocorticoid
Apart from prolactin what other hormone can increase secretion of prolactin
Thyrotropin releasing hormone
Why would cushings cause hypokalaemia
High conc of cortisol displays mineralocorticoid activity by binding to and activating Na/K pumps resulting in hypokalaemia.
What are the main hormones of the menstrual cycle
LH, FHS, oestrogen and progesterone
What are the two parts of the menstrual cycle and their respective lengths
- Follicular phase (14 days although can vary)
- Luteal phase (14 days)
What does FSH do
Stimulates further development of mature follicles and stimulates granulosa cells to release oestrogen in a negative feedback loop to suppress LH and FSH
What causes the follicle to release an ovum and what day does this happen on
Drop in oestrogen and rise in LH on day 14
What is the corpus luteum
Follicle which has released the ovum
What does the corpus luteum release
Progesterone (steroid sex hormone) and oestrogen
What does a fertilised corpus luteum cause
Embryo to produce HCG and this can be detected in a pregnancy test
What does an unfertilised corpus luteum cause
A drop in progesterone and oestrogen stopping the negative feedback loop causing LH and FSH to rise and menstruation to occur
What do leydig cells secrete
Produces testosterone
Where is sperm produced
Testes
What is found in the seminiferous tubules
Sertoli and Leydig cells
What does sertoli cells produce
Androgen binding protein
What do leydig cells produce
Testosterone
What stimulates leydig cells
Leutinizing hormone
What stimulates sertoli cells
FSH
What days are females most fertile in their menstrual cycle
The middle- 9-16 days
Other than PCOS what is heavy menstruation associated with
Hypothyroidism
What electrolyte abnormality can insulin cause
Hypokalemia
Treatment for toxic multinodular goitre
Radiodine therapy
What is medullary thyroid cancer
Cancer of the parafollicular cells that secrete calcitonin
