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Chapter: Paediatrics: Endocrinology and diabetes

Paediatrics: Hypocalcaemia

Most causes of low calcium (hypocalcaemia) can be explained by abnor-malities of vitamin D or PTH metabolism or by disordered kidney func-tion.



Most causes of low calcium (hypocalcaemia) can be explained by abnor-malities of vitamin D or PTH metabolism or by disordered kidney func-tion. The principal manifestations of hypocalcaemia are related to neuro-muscular irritability and include tetany and paraesthesiae.


·  Hypocalcaemic seizures (grand-mal type) or laryngeal spasm may occur acutely.


·  Cardiac conduction abnormalities (prolonged QT interval, QRS and ST changes, and ventricular arrhythmias) may be seen.


Chronic hypocalcaemia may be asymptomatic. The child’s age is helpful in determining the differential diagnosis of hypocalcaemia.


Causes of hypocalcaemia


Early neonatal causes


·  Prematurity


·  Maternal diabetes


·  Maternal pre-eclampsia


·  RDS


Late neonatal causes


·  Cow’s milk hyperphosphataemia


·  Maternal hypercalcaemia


·  Congenital hypoparathyroidism


Causes in infancy


·  Nutritional rickets


·  Pseudohypoparathroidism type 1a


Childhood causes


·  Pseudohypoparathyroidism type 1b


·  Hypoparathyroidism


Iatrogenic causes


·  Chemotherapy agents, e.g. cisplatin


·  Anticonvulsant agents, e.g. phenytoin




·  Plasma calcium.


·  Plasma phosphate.


·  Serum PTH. Note: Low or even normal PTH concentration implies failure of PTH secretion.

·  Plasma vitamin D.


·  Plasma magnesium.


·  X-ray of skull. Chronic hypocalcaemia: basal ganglia calcification may be seen.




Acute treatment


Chronic treatment


·Should be directed at the underlying cause.


·Oral calcium supplements, together with oral vitamin D therapy in the form of calcitriol (1-A calcidiol) are often required to maintain plasma calcium levels within the normal range.




Low serum parathyroid hormone levels in childhood may be due to the following:

·Failure in parathyroid development (agenesis/dysgenesis):


·  isolated defect: X-linked recessive;

·  associated with other abnormalities, e.g. DiGeorge syndrome, Kearnes–Sayre syndrome.


·Destruction of parathyroid glands:


·  autoimmune—type 1 autoimmune polyendocrinopathy;

·  surgery (post-thyroidectomy);

·  radiotherapy.

·Failure in PTH secretion: magnesium deficiency.


·Failure in PTH action: pseudohypoparathyrodism.




·Plasma calcium: low.


·Plasma phosphate: high.


·Serum PTH: low.


Pseudohypoparathyroidism (PHP)


Characterized by end-organ resistance to the actions of PTH. It is a genet-ic disorder due to a defect in the Gs A-adenylate cyclase signalling system common to the PTH receptor and other endocrine receptors belonging to the G protein-receptor family (e.g. TSH, LH, FSH). See Table 12.2.


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