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17 Cards in this Set
- Front
- Back
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Where is Vitamin D produced and what is its function? |
Vitamin D is produced in the kidneys and increases absorption of Ca2+ from intestines (↑ Ca2+ levels in blood) (and other elements). Therefore helping with bone development. |
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How is Vitamin D synthesised? |
1. Sunlight causes skin to prod cholecalciferol (Vit D3). 2. Cholecalciferol (Vit D3) goes to liver to be conv to calcidiol (25-hydroxyvitamin D). 3. Calcidiol goes to kidneys to be conv to calcitriol (1,25-hydroxyvitamin D) (vitamin D). |
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Which form of Vitamin D is active and which form is usually clinically measured? |
Vitamin D (calcitrol; 1,25-dihydroxyvitamin D) is the active form. Calcidiol (25-dihydroxyvitamin D) is the one clinically measured. |
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What is Hereditary Vitamin D Resistant Rickets (HVDRR)? |
It is an autosomal recessive disorder that results from defective Vit D receptor. |
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How does HVDRR differ from nutritional rickets? |
HVDRR: - ↓Ca2+ levels in blood - Normal calcidiol (25(OH)vitamin D3 - ↑ calcitriol (1,25; active Vitamin D) (because not used by defective receptors) Nutritional Rickets: - ↓ calcidiol and calcitriol - ↑ Alkaline phosphatase (increased bone turnover) - Secondary hyperPTHism (↑PTH because of negative feedback PTH stim when there's low Ca levels so PTH can break down bone to release more Ca into blood). |
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How might a patient with HVDRR present and why? |
1. Short stature (because of ↓ Ca2+) 2. Bow legged (because of ↓ Ca2+) 3. Alopecia |
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How can you treat a patient with HVDRR? |
- Oral supplements of Vit D - Oral/IV Ca2+ |
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Where are glucocorticoids produced and what are they for? |
Glucocorticoids (e.g. cortisol) are produced at the adrenal cortex and are for glucose regulation (↑ gluconeogenesis, ↑ blood glucose levels) and inflammation. |
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What is glucocorticoid resistance? |
Glucocorticoid resistance is an autosomal disorder where the cortisol prod by the adrenals has abnormal negative feedback to the hypothalamus to stop CRH production. (In normal negative feedback, cortisol only stops ant pituitary gland from prod ACTH.) |
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What happens to hormone levels in glucocorticoid resistance? |
1. ↑ serum cortisol concentration (because accumulate due to defective receptors)
2. Normal ACTH |
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How might a patient with glucocorticoid resistance present? |
1. Chronic fatigue 2. Asymptomatic (no signs of Cushing's or Addison's) 3. Hypokalaemic alkalosis; Hypertension (because cortisol has intrinsic mineralocorticoid activity so raised cortisol will cause these problems). 4. Masculinisation (hirsutisim, menstrual irregularities and infertility) 5. Hyperandrogenism in men 6. Precocious puberty in children
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How can you treat glucocorticoid resistance? |
Synthetic glucocorticoids (with minimal mineralocorticoid activity) (e.g. dexamethasone) --> Higher than normal dose because their adrenals are not suppressed by dexamethasone) |
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What is androgen insensitivity syndrome? |
It is a X-linked gene mutation that leads to abnormal androgen receptors and androgen resistance. Outward looking female with male genes. |
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What is the active form of testosterone? |
DHT (5-alpha-dihydrotestosterone) |
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How might a patient with androgen insensitivity syndrome present? |
1. Primary amonorrhoea (because no ovaries) 2. Breast development (because body doesn't react to testosterone so present as female) 3. No pubic hair 4. Tall stature |
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What is McCune Albright Syndrome? |
McCune Albright syndrome is a random mutation (mosaicism) of the neural crest cells during embryogenesis --> mutation of the alpha subunit of Gs --> adenylyl cyclase continuously turned on --> increased cAMP --> overproduction of hormones. |
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How might a patient with McCune Albright syndrome present? |
1. Abnormal bone growth 2. "Cafe au lait" spots 3. Endocrine problems (precocious puberty, thyroid problems, acromegaly, cushing's like syndrome) |
