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448 Chapter 11: Endocrine system

are severe symptoms or signs such as confusion, in- Investigations
travenous saline together with iv furosemide are used. Low or normal serum calcium, with a raised PTH.
Potassium and magnesium often fall and need supple- Phosphate is high. Skeletal X-ray classically shows sub-
ments. Bisphosphonates may also be used, although periosteal erosions, ‘brown tumours’ which are areas
they can take some time to act. of radiolucency which mimic lytic bone lesions and a
If surgery is not possible, oral phosphates or bispho- ground-glass appearance of the skull.

sphonates reduce bone resorption and osteoclast ac-
tivity.
Management
Dietary calcium and Vitamin D supplements. For renal
patients alfacalcidol and calcitriol are suitable forms of
Secondary hyperparathyroidism
vitamin D, as they do not require hydroxylation by the
Definition kidney to become active.
This is a syndrome of appropriately raised parathyroid
hormone (PTH) in response to hypocalcaemia.
Tertiary hyperparathyroidism

Incidence/prevalence Definition
Increasing because of survival of renal patients on dial- Development of parathyroid hyperplasia or adenomas
ysis. and autonomous parathyroid hormone (PTH) secretion
following chronically low calcium levels.
Aetiology
Common causes of chronic hypocalcaemia are chronic Aetiology
renal failure and vitamin D deficiency. Any cause of chronic secondary hyperparathyroidism, in
particular chronic renal failure. Often becomes apparent
post-renal transplantation.
Pathophysiology
1 Chronic renal failure leads to reduced hydroxyla-
tion of inactive vitamin D (25-hydroxycholecalciferol Pathophysiology
25(OH)D 3 )to the active vitamin D (calcitriol or During secondary hyperparathyroidism, the glands may
1,25(OH) 2 D 3 )in the kidney, and hence a functional become autonomous, either developing an adenoma
vitamin D deficiency. or hyperplasia which secretes excessive PTH resulting
2 Chronic hypocalcaemia caused by vitamin D defi- in hypercalcaemia. In a patient with renal failure and
ciency stimulates chronically increased parathyroid secondary hyperparathyroidism who undergoes renal
hormone secretion, which may cause some restora- transplantation, PTH secretion may fall as the glands
tion of serum calcium. The failing kidney also retains recover normal activity.
phosphatewhichbindscalcium,reducingserumlevels
further. Clinical features
3 The pathological effects are due to raised PTH levels History of previous secondary hyperparathyroidism.
which cause loss of calcium from the skeleton. Clinical features are those of hypercalcaemia (bones,
stones, groans and moans).
Clinical features
This condition is usually asymptomatic and chronic,
Complications
although hyperparathyroidism may cause vague bone
Acuteseverehypercalcaemiamaycauseseizures,abdom-
pains. Hypocalcaemia is rarely severe.
inalpain,nauseaandvomiting,confusionandpyschosis.
Complications
Tertiary hyperparathyroidism (hypercalcaemia due to Investigations
autonomous parathyroids). Hypercalcaemia with markedly raised PTH.