Let's go through the causes of hypocalcemia.
Parathyroid surgery and the hungry bone syndrome
are classic causes of low serum calcium.
Patient's who've had neck irradiation, likewise
may have damage to their parathyroid gland,
also immune damamge to the thyroid gland as well,
infiltrative diseases of the thyroid gland
as one may rarely see in cases
of sarcoidosis or lymphomas,
hemochromatosis or Wilson's disease,
pseudohypercalcemia caused by low albumin state,
patients with malignancies
those individuals with vitamin D deficiency or low magnesium,
as well as patients with pancreatitis who can have
saponification of calcium within the gland due to
extreme exacerbations that lead to a low serum calcium.
Rhabdomyolysis is another classical example
as is most causes of kidney injury
and finally, the tumor lysis syndrome.
The clinical features of hypercalcemia are
also based on the level of calcium obtained.
There really are minimal symptoms when the
level lies in the range of 7.5 to 8.9 mg/dL
Most patients report symptoms of intermittent
paresthesias of the hands or feet or perioral numbness.
Hypocalcemia due to chronic hypoparathyroidism
can also be associated with cataract formation,
basal ganglia calcification, papilledema
and dental enamel hyperplasia.
As the calcium level decreases further, patients
may present with neuromuscular symptoms and signs.
Carpopedal spasms is the classic example.
Here there is flexion at the metacarpophalangeal
joints and extension at the interphalangeal joints.
Spontaneous or triggered by transient distal
limb ischemia during blood pressure assesment
can cause this carpopedal spasm, and this is
classically known as Trousseau's sign.
Facial nerve hyperirritability and muscle spasm
demonstrated by percussion of the facial nerve
just anterior to the ear is
known as Chovstek's sign.
Laryngospasm, seizures and even myocardial
dysfunction which may cause sudden cardiac death
due to severe hypocalcemia usually occur
in ranges of calcium lower than 7.5 mg/dL