Parathyroids Flashcards
What is the main function of parathyroid hormone ?
To increase Calcium concentrations
What does PLC do?
Inhibits PTH release
How is PLC controlled?
CASR calcium sensing receptor
Activation increases PCL secretion
What is CASR
A G protein coupled receptor
What are the four symptoms of Hypercalcaemia
Bones
Stones
Abdomina groans
Psychic moans
Acute signs of Hypercalcemia
Thirst
Dehydration
Confusion
Polyuria
Chronic signs of Hypercalcemia
Myopathy Fractures Osteopenia Depression Hypertension Pancreatitis
What drugs can cause Hyperparathyroidism?
Vitamin D supplements
Thiazides
List some causes of Hyperparathyroidism
Malignacy
Granulomatous diseases
High bone turn over
Familial
How does malignancy cause Hyperparathyroidism?
Metastatic bone destruction
PTHrp from solid tumours
Osteoclast activating factors
How can a malignant hyperparathyroidism be diagnosed?
Increased Ca2+ and alkaline phosphatase
X ray CT or isotope bone scan
What can lead to a high bone turn over?
Bed ridden
Pagets
Thyrotoxicosis
What are the signs of a primary hyperparathyroidism?
Raised serum Ca2+
Raised Serum PTH
Increased urinary Ca2+ excretion
What is the acute treatment for Hyperparathyroidism?
0.9% saline 4-6L in 24 hrs Loop diuretics Bisphosphonates Steroids Sodium Calcitonin Chemotherapy
What diuretic should be avoided in the acute treatment of hyperparathyroidism?
Thiazide
When are steroids used and what is the first line?
Used in granulomatous diseases like sarcoid
Prednisolone 40 mg
Sodium calcitonin usage
Rarely used
In what circumstances is a parathyroidectomy undertaken?
End organ damage
Serum Calcium over 2.85
What is end organ damage in relation to Hyperparathyroidism?
Bone disease Brown Tumour Pepper pot skull Gastric ulcers Renal stones
Along with a high calcium what else must there be to undergo a parathyroidectomy?
Serum Calcium over 2.85
Under 50
eGFR <60ml/min
What indicates a secondary Hyperparathyroidism
Low serum Ca2+
High PTH
What is a secondary Hyperparathyroidism?
Physiological response to low Ca2+ or Vitamin D
What indicates a tertiary Hyperparathyroidism?
High Ca2+ and PTH
What is tertiary hyperparathyroidism?
Parathyroid has become autonomous due to chronic overactivity
What genetic links does hyperparathyroidism have?
Links to MEN1/2
Why will most people with MEN1/2 have Hyperparathyroidism?
Most will have a parathyroid adenoma
As a result of the adenoma what will most MEN1/2 patients be affected by?
Hypercalcemia by a young age
What is Hypocalciuric Hypercalcemia
Familial autosomal dominant
Usually benign asymptomatic
What is the pathology behind Hypocalciuric Hypercalcemia?
Deactivation of the CaSR channels
No PLC release
What are the symptoms of Hypocalciuric Hypercalcemia?
Mild Hypercalcemia
Reduced Ca2+ urinary excretion
PTH slightly elevated
Signs of hypocalcaemia
Parasthesia - fingers toes personally Fatigue Fits Muscle weakness, cramps, Tetany Bronchospasm
On an ECG how may hypocalcaemia manifest?
Prolonged QT
What is the acute treatment for hypocalcaemia?
IV Calcium Gluconate
Causes of hypoparathyroidism
Congenital - Digeorge syndrome
Destruction- Surgery Radio/chemotherapy
Autoimmune
Hypomagnesaemia
Management of hypoparathyroidism
> 1-2g of Calcium supplement
Vitamin D supplement
What Vitamin D supplements are there?
Alphacalcidol
Cholecalciferol- Injection 6 monthly
Why does hypomagnesaemia cause low Ca2+ levels?
Ca2+ release from the parathyroid is dependent of Mg+
Biochemically how does hypomagnesaemia present?
Intracellular Ca2+ is high
Low PTH
What can cause hypomagnesaemia?
Thiazides PPI GI illness Pancreatitis Malabsorption
What is diabetes insipidus?
Failure of the body to concentrate the urine
NO link to diabetes mellitus
What are the two types of diabetes insipidus?
Nephrogenic - caused by fault within the kidneys
Neurogenic - caused by fault within the brain
List some nephrogenic causes of diabetes insipidus
Lithium usage
Electrolyte imbalance
Kidneys unresponsive to ADH
What electrolyte imbalance could lead to nephrogenic diabetes insipidus?
Low K+ High Ca+
List some neurogenic causes of diabetes insipidus
Lesion
Tumour
Autoimmune
Head injury
How do you work out the serum osmolarity?
[Na+ + K+]² + urea + glucose
What is the normal serum osmolarity of the urine?
275-295 mmol/L
What is the definition of diabetes insipidus?
High plasma osmolarity + urine osmolarity is low
What is the definitive test for diabetes insipidus?
Water deprivation test
