EMQs in Clinical Medicine.pdf - Peshawar Medical College

206 Metabolic and endocrine disturbances
D
J
Patients on TPN for a long period of time are at risk of becoming zinc
deficient. Patients with zinc deficiency have these characteristic crusted
lesions around the mouth and nostrils.
A 45-year-old woman presents with thirst, abdominal pain and history
of renal stones.
There are numerous causes of hypercalcaemia, including malignancy,
primary hyperparathyroidism, sarcoidosis and thyrotoxicosis. Initial
management consists of aggressive rehydration with intravenous fluids.
Further therapy is directed at treating the underlying cause where possible.
Bisphosphonates are also useful in treating hypercalcaemia associated
with malignancy. They act by inhibiting osteoclast resorption of bone
and hence lower serum calcium levels.
81 Disorders of sodium balance
Answers: E B L J C
E
B
A 55-year-old smoker presents with weight loss, haemoptysis and
confusion. Urine osmolality 520 mosmol/kg and serum sodium
112 mmol/l.
Syndrome of inappropriate ADH secretion (SIADH) is particularly associated
with malignancy, especially small cell carcinoma of the lung. Other
notable tumours include those of the central nervous system (CNS),
prostate, pancreas, thymus and lymphomas. To make the diagnosis patients
must be clinically euvolaemic with normal thyroid and adrenal function, a
low plasma osmolality and inappropriately high urine osmolality.
Other causes of SIADH include head injury, CNS disorders, e.g.
meningoencephalitis, and metabolic disease, e.g. porphyria.
Drugs that can cause SIADH include carbamazepine, chlorpropamide and
cyclophosphamide.
A 30-year-old man presents with symptoms of polyuria and polydipsia.
Plasma sodium 165 mmol/l, plasma osmolality 310 mosmol/kg,
urine osmolality 190 mosmol/kg.
Diabetes insipidus (DI) is characterized by impaired water resorption by
the kidney as a result of lack of ADH secretion by the posterior pituitary
(cranial DI) or reduced sensitivity of the kidneys to the action of ADH
(nephrogenic DI).
Biochemistry reveals a high/borderline high plasma osmolality (patient
always feels thirsty and tries to replace the lost fluid and lower plasma
osmolality) with a low urine osmolality (the patient complains of
production of large amounts of very dilute urine as a result of reduced
water resorption in the kidney).