Page 453 - Medicine and Surgery

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Chapter 11: Disorders of the parathyroids 449

Management Clinical features
Total parathyroidectomy possibly with autotransplanta- Hypocalcaemiaandalkalosiscauseincreasedneuromus-
tion of parathyroid tissue equivalent to a normal gland cularexcitability:paraesthesiasofthefingertipsandtoes,
into the arm, where it can be readily accessed for further tetany (spasms of muscles of extremities and face)
treatment. Calcium replacement, phosphate binders and Trousseau’s sign: Inflating a blood pressure cuff to
alfacalcidol(1-alphahydroxyvitaminD 3 )toincreasecal- above systolic BP for at least 2 minutes causes carpal
cium absorption and serum levels may be effective by spasm, which does not relax for a few seconds after
negative feedback on the parathyroids. deflation.
Chvostek’s sign: Tapping the facial nerve anterior to

the ear lobe causes twitching of the facial muscles.
Hypoparathyroidism Convulsions occur more commonly in young people.
Definition
Adeficiency of parathyroid hormone (PTH) char- Investigations
acterised by hypocalcaemia and hyperphosphataemia, Low calcium with normal or high phosphate with no
with normal renal function. detectable PTH on immunoassay. Alkaline phosphatase
is normal. U&Es should be normal, or a renal cause is
suspected.
Aetiology
Most commonly occurs following surgery with removal
Management
of abnormal parathyroid glands or removal of neck ma-
Replacementtherapywith1,25(OH) 2 D 3 (calcitriol,vita-
lignancies.Glandfailuremaybecausedbydirectdamage
min D 2 )or 1(OH)D 3 .Serum and urinary calcium must
to the glands or their blood supply.
be measured, as hypercalcaemia and hypercalciuria can
Idiopathic hypoparathyroidism:
occur. Vitamin D intoxication causes irreversible renal
Genetic abnormalities are usually autosomal recessive

damage. Thiazide diuretics which increase renal tubular
and manifest at an early age. Associated with autoan-
reabsorption of calcium may be useful in treating hyper-
tibodies specific for parathyroid and adrenal tissue.
calciuria.
Associated autoimmune syndromes include perni-

cious anaemia, ovarian failure, autoimmune thyroidi-
tis, and diabetes mellitus. Prognosis
Late onset idiopathic hypoparathyroidism occurs
Lifelong treatment and follow-up.
without circulating autoantibodies.
Functional hypoparathyroidism occurs in patients with Pseudohypoparathyroidism
chronic hypomagnesaemia which results in a failure of
PTH release. Definition
This is a rare condition in which there is impaired re-
sponse to circulating parathyroid hormone, and hence
Pathophysiology
hypocalcaemia and hyperphosphataemia.
PTH is normally released in response to hypocalcaemia,
to restore calcium levels. The consequences of reduced
PTH are decreased calcium levels, increased phosphate Aetiology
levels, decreased 1,25(OH) 2 D 3 and alkalosis (due to de- Failure of the target cell response to parathyroid hor-
creased bicarbonate excretion). mone, thought to be due to a PTH receptor defect or
In chronic cases of hypoparathyroidism, calcification
its coupling to the second messenger system, adenylate
of the basal ganglia causing extrapyramidal signs and cyclase.
calcification of cornea may occur.
Cardiovascular problems with prolongation of the QT Clinical features

interval in ECGs associated with hypocalcaemia, hy- Round face, short stature with short fourth and fifth
potension and refractory congestive heart failure. metacarpals and metatarsals. Other features are the same