Page 450 - Medicine and Surgery

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446 Chapter 11: Endocrine system

After8 hours, the patient is allowed to drink freely Primary hyperparathyroidism
and desmopressin (DDAVP – desamino-D-arginine
Definition
vasopressin, a long-acting vasopressin analogue) is
Primary oversecretion of parathyroid hormone (PTH)
given intranasally or i.v. Urine output is monitored.
by the parathyroid glands.
If the kidneys are then able to produce concentrated

urine the diabetes insipidus is due to ADH deficiency,
i.e. central diabetes insipidus. If the urine remains di- Incidence/prevalence
lute the kidneys are insensitive to ADH, i.e. nephro- Common amongst middle-aged and elderly. In patients
genic diabetes insipidus. over the age of 40, incidence may be as high as 1 in 1000
to 1in 2000.
Management
Age
Any underlying cause should be sought and treated if
Increases with age.
possible. DDAVP intranasally is used in cranial diabetes
insipidus. There is no specific treatment for nephrogenic
diabetes insipidus. Sex
2–4F : 1M

Disorders of the parathyroids Aetiology
Neoplasia of the parathyroid gland(s). There are thought
to be genetic and environmental predisposing factors in-
Hyperparathyroidism cludingafamilyhistoryofMultipleEndocrineNeoplasia
(see page 450) and neck irradiation.
Definition
Single benign adenoma 75%
Increasedsecretionofparathyroidhormone(PTH)from
Multiple adenomata or hyperplasia 24%
the parathyroid glands located on the posterior surface
Parathyroid carcinoma 1%
of the thyroid gland.
Pathophysiology
Aetiology Autonomous hypersecretion from one or more glands
Hyperparathyroidism may be primary, secondary or ter- result in hyperparathyroidism, with hypercalcaemia, hy-
tiary (see Table 11.16). Secretion of PTH like peptide is pophosphataemia and osteoporosis.
seen in squamous cell bronchial carcinoma (see page
134).
Clinical features
Presentation ranges from asymptomatic (diagnosed in-
Pathophysiology cidentally on a calcium measurement) to severe and life-
PTH is an 84 amino acid polypeptide, which controls threatening hypercalcaemia. Patients commonly remain
normal calcium homeostasis (see Fig. 11.13). asymptomatic for many years, then develop insidious

Table 11.16 Causes of hyperparathyroidisim
Type Causes
Primary hyperparathyroidism Primary tumour or hyperplasia of the parathyroid gland(s)
Secondary hyperparathyroidism Appropriate increased PTH in response to prolonged hypocalcaemia or vitamin D
deficiency especially in chronic renal failure
Tertiary hyperparathyroidism Prolonged secondary hyperparathyroidism, causing autonomous secretion of PTH and
hypercalcaemia
Pseudohypoparathyroidism End-organ resistance to PTH leads to hypocalcaemia and therefore increased PTH occurs