Endo - general Flashcards
Drugs that can cause DI
- Lithium
- Gentamicin
- Rifampin
- Colchicine
- Cisplatin
- Demeclocycline
- Orlistat
Drugs that can cause T2DM
- Thiazide diuretics
- Corticosteroids
- Atypical anti-psychotics
- Antiretroviral protease inhibitors
Complications of DKA
- Cerebral oedema (mannitol infusion, mechanical ventilation)
- Pulmonary oedema
- ARDS
treatment related reduction in colloid volume –> water accumulation in the lungs –> decreased lung compliance + hypoxaemia
monitor blood O2 levels, lower fluid intake, replace colloid - Iatrogenic hypoglycaemia
- Iatrogenic hypokalaemia
- Arterial/venous thromboembolism
- prophylatic heparin
- gastric stasis
Plasma osmolarity equation
2 (Na+K) + glucose + urea
Anion gap equation
Generally used formula, K is excluded on the grounds that its value is small enough to be disregarded
Na - (Cl + HCO3)
Formula used when the value of the K is expected to vary significantly as in renal patients (+ is the one that is on bb)
(Na + K) - (Cl+ HCO3)
Describe the plasma osmolarity in DKA + HONK
Increased in both DKA + HONK (both are hyperosmolar states)
Much higher in HHS/HONK
o >290 mOsm/kg + ketonaemia/ketonuria - DKA
o >320 mOsm/kg + no significant ketonaemia/ketonuria - HHS/HONK
Actions of insulin
- Glucose uptake
- Increase in glycogen synthesis
- Decreased gluconeogenesis and glycogenolysis
- Increase fat synthesis
- Decreased lipolysis
- Increased amino acid uptake
- Decreased proteolysis
- Increased potassium uptake
- Increased phosphate uptake
- Decreased renal sodium excretion
Factors that
- Increase Ca
- Derease Ca
and where are they produced
Increase
- Calcitriol (skin + UV light)
- PTH (parathyroid glands)
Decrease
- Calcitonin (parafollicular cells of thyroid gland)
How does vitamin D get converted to active Vitamin D (calcitriol)?
Diet + UV light form vitamin D (skin)
25 hydroxylase turns vitamin D to 25-hydroxyvitaminD3 (liver)
1a-hydroxylase turns 25-hydroxyvitamin D3 into 1,25-dihydroxyvitaminD3 (calcitriol, activated vitamin D) (kidney)
PTH increases renal production of 1,25-dihydroxyvitaminD3
Function of PTH on kidneys, bone, small intestines
+ resultant effect
Kidneys
1a hydroxylase stimulation
Increase calcium absorption
Increase phosphate excretion
Bone
Increased bone resorption
Intestines
Increased calcium absorption
Increased phosphate absorption
Resultant effect
- Increased Calcium
- Decreased phosphate
Calcitriol raises blood calcium levels more than PTH
Function of calcitriol/Vitamin D on kidneys, bone, small intestines
+ resultant effect
Kidneys
Increase calcium absorption
Decreased phosphate reabsorption
Bone
Increased bone resorption
Intestines
Increased calcium absorption
Increased phosphate absorption
Resultant effect
- Increased Calcium
- Decreased phosphate
Calcitriol raises blood calcium levels more than PTH
Which 2 substances provide negative feedback to the parathyroid gland?
High Calcium
High Calcitriol
Which substance should be used to monitor vitamin D levels?
25-hydroxyvitamin D
- Major circulating form of vitamin D used to determine vitamin D status
NOT 1,25-dihydroxycholecalciferol
Causes of secondary hyperPTH
- Vitamin D deficiency Poor sunlight Poor dietary intake Malabsorption - CKD - Liver disease
Endo causes of proximal myopathy
- Cushing’s
- Osteomalacia (2ndary hyperparathyroidism)
- Thyrotoxicosis (hyperthyroidism enhances metabolism of 25-hydroxyvitamin D)
What is MEN 1?
Pituitary tumours
Pancreatic tumours
Parathyroid gland hyperplasia
What is MEN2A?
Medullary thyroid cancer
Phaechromocytoms
Parathyroid gland hyperplasia
What is paget’s disease?
- Disease of bone remodelling
- Excessive bone resorption followed by excessive bone growth
- Results in abnormal “mosaic pattern” of lamellar bone (new bone that is being build is woven and not lamellar)
- The marrow spaces are filled by an excess of fibrous tissue with a marked increase in blood vessels
- This leads to skeletal deformities and potential fractures
- Most often it involves the skull, lumbar vertebrae, pelvis, femur
Which are the three main phases of Paget’s disease?
- Lytic phase - osteoclasts - demineralisation + bone resorption
- Mixed phase - lytic phase + blastic phase (rapid disorganized proliferation of new bone tissue by osteoblasts)
- Sclerotic phase - bone formation exceeds bone resorption - structurally disorganised bone (weaker than normal healthy bone, woven bone not lamellar)
- Burned out state - osteoblastic activity slows down + there is a dormant state in the disease
Definition of osteoporosis
reduced bone density resulting in bone fragility and increased fractured risk
T-score < -2.5
What is the difference between the T score and the Z score in a DEXA scan?
What does a T-score of < -2.5 mean?
o T score = the number of S.D. the bone mineral density measurement is above or below the YOUNG NORMAL mean bone mineral density
Used to define osteoporosis
o Z score = the number of S.D. the measurement is above or below the AGE-MATCHED mean bone mineral density.
Used to identify patients who may need a work-up for secondary causes of osteoporosis
T-score of < -2.5 = means 2.5 SD or more below the young adult reference mean i.e. less than -2.5 SD therefore -3.5, -4.5 etc
List some RF for osteoporosis
Primary - post menopausal, old age >50 years
Secondary
Drugs - steroids, thyroxin
Endo - Cushing’s, primary hyperparathyroidism, hyperthyroidism, hypogonadism
Cancer - myeloma, metastatic carcinoma
MSK - RA, ankylosing spondylitis, SLE
GI - coeliac disease, IBD
- Post-menopause
- Primary hypogonadism/Secondary amenorrhea – low oestrogen can lead to decreased bone mineral density
- Late menarche/early menopause
- Corticosteroid use (antagonise vitamin D and therefore decrease calcium absorption from the gut)
- Glucocorticoid excess e.g. Cushing’s syndrome
- Vitamin D deficiency
- Low calcium intake
- Prolonged immobilisation/Physical inactivity
- Low BMI
- Smoking, Alcohol
- FHx
- F>M
- > 50 women
- > 65 men
- Afro-carribeans have a higher bone mass than Caucasians
Function of excess PTH
- Stimulates osteoclasts to break down bone
* Makes kidneys hold on to calcium + get rid of phosphate - hypercalcemia, hypophosphatemia
What causes primary hyperparathyroidism?
Parathyroid adenoma
Parathyroid hyperplasia
Parathyroid carcinoma
Parathyroid gland makes PTH independently of the calcium level
RF – MEN1, MEN2A, HTN
What causes tertiary hyperparathyroidism?
- Individuals who have had secondary hyperparathyroidism for many years develop primary hyperparathyroidism
- Chronic stimulation of the parathyroid gland by low Ca results in autonomous PTH secretion even after the cause of hypocalcaemia has been corrected
- Makes PTH independently of calcium levels –> hypercalcaemia
Causes of vitamin D deficiency
• Poor sunlight
• Poor dietary intake
• Malabsorption
• Old age
o Decreased ability of skin to produce vitamin D
• Obesity – body fat stores vitamin D
• CKD
• Granulomatous diseases (e.g. sarcoidosis, TB) – enhanced destruction of Vitamin D
• Hyperthyroidism – enhances metabolism of 25-hydroxyvitamin D
• Medication use – glucocorticoids, antiepileptic medication, rifampicin, St John’s wort
vitamin D deficiency = secondary hyperparathyroidism = osteomalacia