Parathyroid disorders Flashcards
What mineral decreases parathyroid hormone secretion?
Calcium
What are some symptoms of hypercalcaemia?
Bones - Bone pain
Stones - Kidney stones
Abdominal groans - Constipation
Thrones - Polyuria
Psychiatric moans - Depression, anxiety
What are some acute signs of hypercalcaemia?
- Thirst
- Dehydration
- Confusion
- Polyuria
What are some chronic presentations of hypercalcaemia?
- Myopathy
- Fractures
- Osteopenia
- Depression
- Hypertension
- Pancreatitis
- Renal calculi
What is hypocalcuric hypercalcaemia?
This is an autosomal dominant, deactivating mutation in calcium sensing receptors
What are some presentations of hypocalcuric hypercalcaemia?
Mild hypercalcaemia
Reduced urine calcium excretion
Marginally elevated PTH
What are soem causes of hypercalcaemia?
Primary and tertiary hyperparathyroidism
Malignancy
Drugs
Granulomatous disease
Hypocalcuric hypercalcaemia
Milk-Alkali syndrome (Too many antacids)
MEN1/2
What are some drugs that can cause hypercalcaemia?
Vitamin D
Thiazides
What are the mechanisms of hypercalcaemia in malignancy?
Metastatic bone restructure, PTHrp release and osteoclast activating factor release by tumours causes increased release of bone stored calcium into the blood
How will hypercalcaemia of malignancy be diagnosed?
Raised calcium
Raised ALP
X-ray, CT, MRI or PET showing tumour
Isotope bone scanning
Give the cause of hypercalcaemia:
High/Normal PTH
High Urine Ca2+ excretion
Primary/Tertiary hyperparathyroidism
Give the cause of hypercalcaemia:
High/Normal PTH
Low urine Ca2+ excretion
Familial Hypocalcuric hypercalcaemia
Give the cause of hypercalcaemia:
Low PTH
High phosphate
Raised ALP (Bone pathology)
Metastases
Sarcoidosis
Thyrotoxicosis
Give the cause of hypercalcaemia:
Low PTH
High phosphate
Low ALP (No bone pathology)
Myeloma
Vitamin D toxicity
Milk-alkali syndrome
How should hypercalcaemia be acutely managed?
Fluids (0.9% saline 4-6L 24hours)
Consider loop diuretics (Not thiazides)
Bisphosphonates
Steroids possible (E.g. Prednisolone in sarcoidosis)
What are some causes of hypocalcaemia?
- Chronic kidney disease
- Congenital absence (DiGeorge syndrome)
- Destruction (surgery, radiotherapy, malignancy)
- Autoimmune
- Hypomagnesaemia - calcium release from cells is dependent on magnesium
- Idiopathic
- Pseudohypoparathyroidism and pseudo-pseudohypoparathyroidism
What are some symptoms of hypocalcaemia?
- Paraethesia - fingers, toes, perioral
- Muscle cramps, tetany
- Muscle weakness
- Fatigue
- Bronchospasm or laryngospasm
- Fits
What are some clinical signs of hypocalcaemia?
- Chovesteks sign - gentle tapping over the facial nerve causes twitching of the ipsilateral facial muscles
- Trousseau sign - inflation of the sphygmomanometer cuff above systolic pressure for 3 min induces tetanic spasm of the fingers and wrist
- ECG - QT prolongation
How is acute severe hypocalcaemia managed?
- IV calcium gluconate 10 ml, 10% over 10 mins (in 50ml saline or dextrose)
- Calcium infusion (10ml 10% calcium gluconate in 100ml infusate, at 50 ml/h)
How is hypocalcaemia treated in the long term?
- Calcium supplement >1-2g PO/day
- Vitamin D
- 1 alphacalcidol 0.5-1 mcg PO/day OR
- Depot injection: cholecalciferol 300 000 units 6 monthly
What is meant by primary hyperparathyroidism?
This is hyperparathyroidism caused by uncontrolled parathyroid hormone produced directly by a tumour of the parathyroid gland (E.g. Parathyroid adenoma)
What metabolic change will result from hyperparathyroidism?
Hypercalcaemia
How is primary hyperparathyroidism diagnosed?
Raised serum calcium
Raised serum PTH
Increased urine calcium excretion
How is primary hyperparathyroidism managed?
Surgical tumour removal
Symptomatic relief with cinacalcet (Calcium mimic)
What is secondary hyperparathyroidism?
This is parathyroid overactivity caused by infusfficient vitamin D or chronic renal failure, which lead to low calcium absorption from the intestines, kidneys and bones, leading to hypocalcaemia
How will secondary hyperparathyroidism show on blood testing?
- Low calcium
- High PTH
How is secondary hyperparathyroidisim managed?
Correcting the vitamin D deficiency or performing a renal transplant to treat renal failure
What is tertiary hyperparathyroidism?
This is parathyroid overactivity that occurs when secondary hyperparathyroidism continues for a long period of time (e.g. renal failure), leading to hyperplasia of the glands
The parathyroid becomes autonomous after many years of overactivity
How will tertiary hyperparathyroidism show on blood tests?
High PTH
High Calcium
How is tertiary hyperparathyroidisim managed?
Surgical removal of part of the parathyroid tissue to return the parathyroid hormone to an appropriate level
What are some functions of parathyroid hormone?
- Osteoclast activation (Increased bone reabsorption and thus calcium release)
- Increased reabsorption of calcium by the renal tubules
- Increased urinary phosphate excretion
- Increased synthesis of active forms of vitamin-D
What is fibrosa cystica?
This is a condition that occurs when unchecked hyperparathyroidism results in overproduction of PTH and continued osteoclasis
What are the 3 main conditions of fibrosa cystica?
Osteoporosis
Brown tumour formation
Osteitis
How do brown tumours form?
Osteoporotic bone is prone to fracture
Associated haemorrhage elicits a macrophage reaction and processes of organisation and repair
This results in a mass of reactive tissue known as a brown tumour
What are some indications of parathyroidectomy?
- End organ damage
- Bone disease
- Gastric ulcers
- Renal stones
- Very high calcium (>2.85mmol/L)
- Under 50 y/o
- eGFR <60mL/min
What are some causes of hypomagnesemia?
- Alcohol
- Drugs - thiazide, PPIs
- GI illness with diarrhoea
- Pancreatitis
- Malabsorption
What are some symptoms of hypomagnesaemia?
- Anorexia
- Nausea and vomiting
- Muscle weakness, lethargy
- Fits
What are some clinical signs of hypomagnesaemia?
- Cardiac arrhythmias
- Positive Chovestek sign and Trousseau sign indicate secondary hypocalcaemia
How is hypomagnesaemia managed?
Magnesium supplementation
Calcium supplementation if needed
What is the main complication of hypermagnesaemia?
Secondary hypocalcaemia
How does hypomagnesaemia lead to hypocalcaemia?
- Calcium release from cells is dependent on magnesium
- In magnesium deficiency intracellular calcium is high
- PTH release inhibited
- Skeletal muscle receptors less sensitive to PTH
What is pseudohypoparathyroidism?
Condition associated primarily with resistance to the parathyroid hormone
Describe the genetics of pseudohypoparathyroidism
Dysfunction of Gs alpha subunit (GNAS 1 gene), which is coupled to the PTH receptor
How will pseudohypoparathyrodisim present?
- Bone abnormalities (McCune Albright)
- Obesity
- Subcutaneous calcification
- Learning disability
- Brachdactyly (shortened 4th metacarpal)
How will pseudohypoparathyroidism show in blood tests?
calcium will be low but PTH concentrations are elevated due to PTH resistance
What is pseudo-pseudohypoparathyroidism?
- Describes the phenotypic defects of pseudohypoparathyroidism (Albright’s herditary osteodystrophy) but without any abnormalities in calcium metabolism
- Individuals with this condition may share the same gene defect as those with pseudohypoparathyroidism and be members of the same families
