Increasing thyroxine requirements in primary hypothyroidism: don't forget the urinalysis!

ABSTRACT

Rising thyroid stimulating hormone (TSH) levels in patients being treated for primary hypothyroidism usually indicate poor compliance with thyroxine therapy. In rare instances, drugs or diseases affecting absorption of thyroxine or drugs that accelerate thyroxine metabolism can manifest in a similar fashion. Nephrotic syndrome is a rare cause of such a presentation though its presence can rapidly be suspected by dipstick urine testing. In this report we describe a patient with long-standing primary thyroid failure whose thyroxine dose requirements increased upon development of massive proteinuria. Biochemical testing and renal biopsy subsequently demonstrated nephrotic syndrome and amyloid deposition in association with myeloma. Dipstick urine testing should be considered in all hypothyroid patients with rising TSH levels, where good compliance with thyroxine therapy is likely.