Hyper and hypocalcaemia Flashcards
Parathyroid anatomy
- Size
- Location, including neighbouring structures
- VAN
4 parathyroid glands
- Size of rice grain (roughly 6mm long)
Location
- Posterior to thyroid, two superior and two inferior.
V- Superior, middle and inferior thyroid.
Sup + middle- drains into IJV
Inferior drains into Brachiocephalic
A- Superior and inferior thyroid
- Sup- from external carotid
- Inf- from thyrocervical
N- Middle cervical ganglion, inferior cervical ganglion
Histology of parathyroid
Cells are densely packed compared to the follicular thyroid cells.
Chief cells
- Produces PTH
Oxyphil cells
Parathyroid hormone
- Secretion
- Function
- Regulation
Secreted from chief cells of the parathyroid gland.
Responsible for the regulation of calcium and phosphate
- Antagonises the function of calcitonin.
- Stimulates osteoclasts to breakdown bone and release calcium= increases calcium.
- Major phosphate regulator, inhibits proximal reabsorption of phosphate in kidneys.
- Activation of Vit D increases intestinal phosphate absorption
Regulation
- Drop in calcium, increases PTH and vice versa.
- Concentration of ionized Ca2+ determines PTH release, sensed by receptors.
Stimulators of PTH secretion
Low ca2+
Mild decrease of Mg
Inhibitors of PTH secretion
High Ca2+
Calcitrol
Severe decrease of Mg2+
Increase in phosphate
Hypocalcaemia
- Limits
- Causes
Serum Ca2+ <2.1
Causes
- Vitamin D deficiency
- Hypoparathyroidism
- Malabsorption (coeliac, crohn’s, bowel surgery)
- Rhabdomyolysis
- Pancreatitis
- CKD
- Hyperphosphataemia
Hypocalcaemia
- Symptoms
- Signs
Reduced calcium lowers threshold potential for APs as it usually blocks Na+ from binding.
- Leads to multiple neuromuscular signs and symptoms
Symptoms and signs
= CATs go numb
- Convulsions
- Arrhythmias
- Tetany
- Numbness in hands, feet, perioral.
Signs
- Tetany
- Depression
- Carpopedal spasm
- Trousseau’s and chvostek’s sign
- Increase QT interval.
Treatment of hypocalcaemia
- Mild
- Severe
Mild
- Oral calcium
Severe
- IV Ca gluconate
Hypercalcaemia
- Range
- Causes
Ca+ >2.6
Causes
- Primary Hyperparathyroidism
- Hypophosphataemia
- Malignancy: bone, myeloma.
- Vit d toxicity
Hypercalcaemia signs and symptoms
Stones, bones, groans, thrones and psychiatric undertones:
Stones= kidney stones, biliary stones
Bones= bone pain
Groans= Abdominal pain, constipation
Thrones= Polyuria
Psychiatric undertones= depression, anxiety, cognitive dysfunction.
Others
- Cardiac arrest
- weight loss, weakness
- vomitting
Primary hyperparathyroidism
- Definition
- Causes
- Signs and symptoms
Excess production of PTH from the PT gland.
- Defined by high Ca2+ and high/normal PTH.
Causes
- Adenoma (most common)
- Hyperplasia
- PT carcinoma
- Multiple endocrine neoplasia
Signs and symptoms
- Signs of hypercalcaemia (stones, bones, groans, thrones and psychiatric overtones)
- Hypertension
Primary hyperparathyroidism investigations
Blood test
- Ca2+= very high
- Low PO4
- Abnormal PTH compared to ca2+ levels (should be low)
-
ECG
- Short QT
- Bradycardia
- 1st degree block
DEXA
- osteoporosis
ALP
- Increased due to bone activity
Treatment of primary hyperparathyroidism
Medical
- Increase fluid intake
- Avoid foods high in Ca2+
- Avoid thiazides
Surgical
- Excision of adenoma
- Indications: high serum or urinary Ca2+, bone disease/ osteoporosis, kidney stones, decreased kidney function, <50
- complications: hypoparathyroidism, recurrent laryngeal n. palsy.
Secondary hyperparathyroidism
- Definition
- Causes
Hypocalcaemia leading to high PTH levels
Causes
- Vitamin D deficiency
- Chronic renal failure
- Malabsorption (crohn’s, coeliac, chronic pancretitis)
Secondary hyperparathyroidism
- Signs and symptoms
Signs and symptoms correspond with signs of hypocalcaemia
Hyperphosphataemia
Treatment of secondary hyperparathyroidism
Correct underlying causue
Phosphate binders
- Calcichew (with Ca0)
- Without ca2+: sevelamer, lanthanum
Vit.D
- Calcitrol (active)
- Cholecalciferol (inactive)
Hypoparathyroidism
- Definition
- Causes
Low PTH due to glandular failure
Causes
- Autoimmune (i.e. autoimmune polyendocrine syndromes)
- Congenital (DiGeorge)
- Iatrogenic: surgery, radiation.
Congenital causes of hypoparathyroidism
DiGeorge’s (Chromosome 22)
Tetrology of Fallot’s
Thymic aplasia
Cleft palate
Secondary hypoparathyroidism
Secondary causes of low PTH
Causes
- Surgery
- Radiation
- Low Mg
Pseudohypoparathyroidism
- Description
- Signs
- Investigation findings
Failure of target cells to respond to PTH due to genetic cause
Signs
- Short 4th and 5th metacarpals
- round face
- short stature
- calcified basal ganglia
Investigations
- PTH elevated
- HypoCa2+
- ALP normal/ elevated
Pseudopseudohypoparathyroidism
- Description
Morphological feature of pseudohypoparathyroidism with normal biochemistry
- Has skeletal defects with normal Ca and PTH
Multiple endocrine neoplasia
- Type 1
Syndrome of hormone producing tumours
- Inherited in autosomal dominant fashion
- MEN-1 is a tumour suppressor gene
MEN-1 tumors
- Parathyroid hyperplasia/ adenoma
- Pancreas endocrine tumours: glucagonoma, gastrinoma, insulinoma.
- Pituitary adenoma
Multiple endocrine neoplasia
- Type 2
MEN-2 cancers
- Thyroid medullary carcinoma
- Pheochromocytoma (benign and bilateral)
- parathyroid hyperplasia
What is the medical treatment of acute, mild hypocalcaemia (>1.9)
Oral calcium supplement
- Adcal, Calcichew
Vitamin D supplement (if they are deficient)
Correct any magnesium deficiency
What is the medical treatment of acute, severe hypocalcaemia (<1.9)
IV calcium replacement
- 10mL of 10% calcium gluconate over 10 mins
- In 50-100mL of 5% dextrose
Follow up with
- 100mL of 10% calcium gluconate
- In 1L of saline
