Adverse effects of steroid excess on bone metabolism are well established but presentation of Cushing's syndrome with metabolic bone disease is reported to be uncommon. We describe a case of Cushing's syndrome presenting with pathological fractures probably present for 8 years before diagnosis.
A 33 year old nurse first sustained spontaneous stress fractures of her metatarsals in 1994, with repeated fractures occurring up to 2002. In 2001 she developed hypertension, acute lumbar back pain and gained weight. In 2002 she was admitted to hospital with chest/back pain. Lumbar spine X-ray showed new fracture of L3,old fractures of L4/5,with fractured ribs on CXR. Isotope bone scan revealed multiple hot spots. MRI showed collapse of T8 with features consistent with malignant disease. The primary malignancy was sought and a left-sided 1.5 centimetre thyroid nodule detected. Suspicious cytology prompted thyroid lobectomy revealing follicular variant of papillary carcinoma. T8 biopsy revealed chronic infection with Propionobacteria rather than metastatic carcinoma. Despite antibiotic therapy further spontaneous vertebral fractures developed. Bone densitometry revealed Z scores of minus 2.4 at L2-4, minus 2.5 and 2.9 at the hips.
Referral to our centre prompted investigations for Cushing's syndrome. Serum potassium was 4.1 millimols per litre, androgens,calcitonin and urinary catecholamines all normal. TSH was suppressed by T4 therapy. Urinary free cortisol values were raised,(563-959 nanomols per 24hours) with loss of diurnal rhythm in cortisol secretion (9am 429-586,midnight 397-431 nanomols per litre)and no suppression on low or high dose dexamethasone. Abdominal CT showed a 3.5 centimetre adrenal mass. These findings were consistent with adrenal dependent Cushing's syndrome. Risedronate and metyrapone were commenced before adrenalectomy, completion thyroidectomy and ablative radioiodine.
Comment: Cushing's syndrome may present with spontaneous fractures in both axial and appendicular skeleton in the absence of marked clinical features. This case demonstrates the importance of thorough investigation of unexplained fractures.