You review a 55-year-old woman with a 6-month history of feeling tired and depressed. She has been constipated for the past 3-months, for which she is taking 15 ml of lactulose twice daily. She is otherwise fit and well and has no past medical history of note. You organise some routine blood tests, the results of which are shown below:
- Hb: 12.2 g/dl (12-15 g/dl)
- MCV: 82 fl (80-100 fl)
- Platelets: 212 x 109/l (150-400 x 109/l)
- Na: 144 mmol/l (135-147 mmol/l)
- K: 4.3 mmol/l (3.5-5.5 mmol/l)
- Urea: 6.1 mmol/l (2.0-6.6 mmol/l)
- Creatinine: 87 mmol/l (75-125 mmol/l)
- Calcium: 2.91 mmol/l (2.05-2.60 mmol/l)
- Phosphate: 0.71 mmol/l (0.8-1.4 mmol/l)
- ALP: 130 IU/l (20-140 IU/l))
- TSH: 3.1 mU/l (0.4-4.5 mU/l)
This lady has both hypercalcaemia and hypophosphataemia evident in her blood results. She also has a history of depression, tiredness and constipation, which is consistent with hypercalcaemia. The key is determining the most likely cause of hypercalcaemia, and there are numerous clues to point you in the right direction.
Primary hyperparathyroidism is the most likely cause in this case. It results in excess production of parathyroid hormone (PTH) and raised serum PTH levels. Biochemically there is usually increased serum calcium and low serum phosphate. Alkaline phosphatase (ALP) levels are often elevated in hyperparathyroidism, although they can remain normal in primary hyperparathyroidism, as in this case.
Although the tiredness and constipation could indicate a diagnosis of hypothyroidism, the TSH is normal in this case, ruling out this as a diagnosis.
Primary hyperparathyroidism is the commonest cause of hypercalcaemia in the UK and the most likely cause of hypercalcaemia in this case. It can be caused by either a single (80-85%) or multiple (5%) parathyroid adenomas or by parathyroid hyperplasia (10-15%).
The definitive treatment of primary hyperparathyroidism is surgical parathyroidectomy.
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