Case Study - An unusual cause of constipation

A case of worsening constipation led Dr Louise Newson to ask for blood tests, with surprising results.

Mrs BT, a 72-year-old retired banker attended one morning for a medication review. She had been taking amlodipine, simvastatin and aspirin for hypertension, which had been very well controlled.

She was normally very spritely when she came for her reviews. However, this time she seemed a little muddled over her medication and more vague than normal.

Over the past few months she had been troubled with worsening constipation and intermittent abdominal pains, which were worrying her, as her husband died last year from metastatic bowel cancer.

Examination was entirely unremarkable. I arranged for her to have some routine blood tests and also referred her urgently for investigations to exclude an underlying bowel malignancy.

I was surprised when her blood results showed a raised calcium of 3.1mmol/l. All other results were normal.

Further blood tests revealed a raised parathyroid hormone (PTH) level. She was then referred to the local endocrinologist for further investigations, and was found to have a parathyroid adenoma, which was removed surgically.

Cause of constipation
PTH increases the release of calcium and phosphate from bone, increases calcium reabsorption by the kidney and increases renal production of 1,25-dihydroxyvitamin D3 (calcitriol), which increases intestinal absorption of calcium. As well as increasing serum calcium, PTH also causes phosphaturia, therefore reducing serum phosphate levels.

Primary hyperparathyroidism occurs in approximately four in 100,000 people.

It affects women twice as frequently as men.

Primary hyperparathyroidism is due to a single parathyroid adenoma in 85 per cent of cases, hyperplasia in around 15 per cent and carcinoma in 1 per cent or fewer.1

Hyperparathyroidism leading to hypercalcaemia can cause the following symptoms:

  • Tiredness, malaise, dehydration;
  • Abdominal pain, constipation, nausea and vomiting;
  • Renal colic, polyuria, polydipsia, nocturia;
  • Bone pain - can lead to bone cysts;2
  • Corneal calcification in longstanding hypercalcaemia;.
  • Neuropsychiatric manifestations including depression and confusion.2

Investigations
Ultrasound can be useful in the preoperative evaluation of patients with hyperparathyroidism and for the localisation of parathyroid adenomas,3 while X-ray imaging of the hands can show subperiosteal resorption of the bone.

Surgery involves removal of an adenoma, or parathyroidectomy or subtotal parathyroidectomy for hyperplasia.

However, even in patients with mild asymptomatic primary hyperparathyroidism, successful parathyroidectomy has been shown to be followed by an improvement in bone mineral density and quality of life.4

In general, surgery is recommended for patients who have:

  • Renal stones or impaired renal function.
  • Bone involvement or a marked reduction in cortical bone density.
  • Marked hypercalcaemia (>3.0mmol/l).
  • Younger patients (<50 years).
  • Patients who have had a previous episode of severe acute hypercalcaemia.

Secondary hyperparathyroidism is actually a physiological compensatory hypertrophy of the hyperparathyroids due to hypocalcaemia, and is usually due to renal failure, deficiency of vitamin D or malabsorption.

Tertiary hyperparathyroidism follows secondary hyperparathyroidism.

The glands become autonomous, producing excessive amounts of PTH even after the cause of hypocalcaemia has been corrected.

  • Dr Newson is a GP in the West Midlands.

References
1. Temmim L, Sinowatz F, Hussein W I, Al-Sanea O, El-Khodary H. Intrathyroidal parathyroid carcinoma: a case report with clinical and histological findings. Diagn Pathol 2008; 3: 46.

2. Hoogendijk W J, Lips P, Dik M G, Deeg D J et al. Depression is associated with decreased 25-hydroxyvitamin D and increased parathyroid hormone levels in older adults. Arch Gen Psychiatry 2008; 65: 508-12.

3. Boudreaux B A, Magnuson J S, Asher S A, Desmond R, Peters G E. The role of ultrasonography in parathyroid surgery. Arch Otolaryngol Head Neck Surg 2007; 133: 1,240-4.

4. Ambrogini E, Cetani F, Cianferotti L, Vignali E et al. Surgery or surveillance for mild asymptomatic primary hyperparathyroidism: a prospective, randomized clinical trial. J Clin Endocrinol Metab 2007; 92: 3,114-21.


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