Hypoparathyroidism
Hypoparathyroidism
is a late complication of the iron overload and/or anaemic thalassemia patient.
The incidence of this complication is 3.6%. The majority present after the age
of 16 years and both sexes are equally affected (De Sanctis, 2008).
The majority of cases show a mild form of the disease accompanied by
paraesthesia. However, hypoparathyroidism may cause various neurological
manifestations, including tetany, seizures, carpopedal spasms, and paresthesia,
and little is known about these associated complications in thalassemic
patients. No relation was found between the serum ferritin level and the degree
of parathyroid gland affection (Angelopoulos et al., 2006).
Hypoparathyroidism and
vitamin D deficiency are common causes of calcium and phosphorous metabolism
disturbance in thalassemic patients, and are an important contribution to the
osteopenia and osteoprosis so often diagnosed. Acute symptoms for parathyroid
disease are uncommon. Annual screening for parathyroid and calcium, calcium and
vitamin D supplementation, and nutritional counseling should be initiated early
(Low, 1997).
Investigations
should begin from the age 16 and should include serum calcium, serum phosphate
and phosphate balance. With cases of low serum calcium and high serum phosphate
levels, parathyroid hormone should also be evaluated. Parathormone may be
normal or low, with low reading for 1, 25 dihydroxycholecalciferol (vitamin D).
Bone radiology shows osteoporosis and malformations (De Sanctis, 1995).
Treatment:
-
Oral administration
of vitamin D or one of its analogue. Some patients require high doses of
vitamin D to normalize the serum calcium level. This should be carefully
monitored, as hypercalcaemia is a common complication of this treatment.
-
Calcitriol, 0.25-1.0
µg, twice daily, is usually sufficient to normalize plasma calcium and
phosphate levels. Weekly blood tests are required at the start treatment,
followed by quarterly plasma and urinary calcium and phosphate measurements.
-
In patients with
persistently high serum phosphate levels, a phosphate binder other than
aluminium may be considered.
-
Tetany and cardiac
failure due to severe hypocalcaemia require intravenous administration of
calcium, under careful cardiac monitoring, followed by oral vitamin D (De
Sanctis, 1995).
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