Endocrine Flashcards
What are the 3 main types of hyperparathyroidism?
1) Primary
2) Secondary
3) Tertiary
What are the 6 main causes of hypercalcaemia?
1) Hyperparathyroidism (1 +3)
2) Malignancy (ectopic PTH-like protein production)
3) Drugs (Thiazides, vit D analogues, Li)
4) XS calcium intake (crohn’s disease, dietary)
5) Familial hypocalciuric hypercalcaemia
6) Long-term immobility
What is the most common cause of hypercalcaemia?
Primary hyperparathyroidism.
80% adenoma, 20% glandular hyperplasia, <0.5% carcinoma
What is the pathophysiology of secondary hyperparathyroidism?
hypocalcaemic parathyroid stimulation –> hyperplasia –> increased PTH secretion
Can be caused by CKD or Vitamin D deficiency
What is tertiary hyperparathyroidism?
Prolonged secondary hyperparathyroidism leading to hyperplasia and an autonomous PTH function
Primary hyperparathyroidism diagnosis + treatment?
High PTH
High Ca2+
Low PO43-
High ALP
No underlying pathology Identify with: PT ultrasound, CT/MRI -Hyperparathyroidectomy -If contraindicated --> take CINACALCET -Avoid thiazides, XS vit D and calcium -Exercise
Secondary hyperparathyroidism diagnosis + treatment?
High PTH
Low Ca2+
High PO43-
High ALP
Treat underlying pathology
Tertiary hyperparathyroidism diagnosis + treatment?
High PTH
High Ca2+
High PO43-
High ALP
Treat prolonged underlying pathology
If not possible –> surgery
What are the main clinical presentations of hyperparathyroidism?
Bones, stones, abdominal groans, psychiatric moans, cardiac tones
Malignant hypercalcaemia diagnosis and treatment?
Low PTH
Low albumin
High ALP
B2 microglobulin
Identify with:
- radioisotope screening
- CT/MRI
Chemo + radiotherapy, surgery
What additional tests can be done in hyperparathyroidism?
TSH levels to exclude hyperthyroidism
DXA bone density scan
24hr urinary Ca2+ (familial hypocalciuric hypercalcaemia)
What 4 things would you do if patient has SEVERE ACUTE HYPERCALCAEMIA?
- IV 0.9% saline: prevent renal calculi
- Bisphosphonates (e.g. IV pamivonate): prevent bone resorption
- Check serum U&E daily and calcium 48hrs after initial treatment
- Give GC (e.g. prednisolone) if e.g. sarcoidosis, myeloma, vit D excess
Why might hypoalbuminaemia cause hypocalcaemia despite no change in free calcium levels?
Because some calcium is albumin bound.
In what group of people is hypocalcaemia most common?
Hospitalised patients
What percentage of intensive care patients have hypocalcaemia?
Up to 88%
Give an aetiological factor of hypocalcaemia.
1) CKD
2) Vitamin D deficiency
3) Hypoparathyroidism (primary and secondary)
4) Pseudoparathyroidism
5) Drugs e.g. Calcitonin, bisphosphonates
6) Pancreatitis or osteomalacia
How does CKD cause hypocalcaemia?
1) Less activation of calcidiol to calcitriol via 1-a-hydroxylase
2) Less gut Ca2+ absorption
What are the 2 forms of primary hypothyroidism and how do they cause hypocalcaemia?
1) Congenital AI DiGeorge syndrome
2) Idiopathic: AI parathyroid Ab’s
- Less PTH –> less Ca2+
What can cause secondary hypoparathyroidism?
- Radiation
- Parathyroidectomy/ Thyroidectomy
- Hypomagnesaemia
Why are PTH levels raised in pseudohypoparathyroidism?
Due to the failure of target organ PTH stimulation, there is no increase in serum Ca2+, so no negative feedback mechanisms are activated to inhibit PTH production.
PTH is continually secreted in an attempt to increase serum Ca2+. (Similar to beta cells insulin secretion in early DMT2)
What are the similarities and differences in pseudohypoparathyroidism and pseudopseudohypoparathyroidism?
Similarities:
- Skeletal defects e.g. shorter 4th and 5th metacarpals
- Subcutaneous calcification
- Short
- Intellectual impairment
Differences:
- Pseudo: High PTH and PO43-, Low Ca2+
- All are normal in pseudopseudoparathyroidism
How might bisphosphonates cause hypocalcaemia?
Inhibit osteoclast activity so prevent bone resorption.
What is significant about the phosphate levels in pancreatitis and osteomalacia?
They are normal or low, despite the low Ca2+.
What are some clinical presentations of hypocalcaemia?
1) Spasms - carpopedal (Trousseau’s sign)
2) Paraoral paraesthesia
3) Anxiety/irritation/irrational
4) Seizures
5) Muscle (smooth) contraction (wheeze)
6) Orientational impairment + confusion
7) Dermatitis/diarrhoea
8) Impetigo Herpetiformis (in pregnancy)
9) Chvodeck’s sign/ cataracts/ cardiomyopathy
What is a positive trousseau’s sign?
A carpopedal spasm when the sphygmomanometer cuff is inflated above systolic BP.
What is a positive Chvodeck’s sign?
When the facial nerve (CN VII) is tapped near the parotid, the IPSILATERAL facial muscles twitch.
What 2 signs are seen in severe hypocalcaemia?
Prolonged QT interval
Papilloedema (^ ICP = optic disc swelling)
How is alkalosis e.g. caused by HYPERVENTILATION, a differential dignosis of hypocalcaemia?
Because albumin becomes more negatively charged and so it binds to more free Ca2+. This means levels of bioavailable Ca2+ is decreased.
How are magnesium or potassium deficiencies differential diagnoses of hypocalcaemia?
Magnesium is required for PTH production.
Mg is also required to transport Ca2+ and K+ into and out of cells.
How do you check for renal impairment as a cause of hypocalcaemia?
- Serum urea
- Serum creatinine
- eGFR
What are PTH, Ca2+, PO43- and AI Ab serum levels in idiopathic primary hypoparathyroidism?
PTH: low
Ca2+: low
PO43-: high
AI Ab: present
What are PTH, Ca2+, PO43- and AI Ab serum levels in secondary hypoparathyroidism?
PTH: low
Ca2+: low
PO43-: high
AI Ab: absent
How do you treat a patient with acute severe hypocalcaemia?
IV CALCIUM GLUCONATE
over 30 minutes, monitor ECG
How do you treat a patient with vitamin D deficiency that does not have hypoparathyroidism?
ORAL CHOLECALCIFEROL (vitamin D3) ORAL ADCAL (vitamin D + Ca2+)
How do you treat a patient with vitamin D deficiency that does have hypoparathyroidism?
ORAL CALCITRIOL
CALCIUM SUPPLEMENTS
