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
