[A pitfall in the treatment of hypothyroidism].

Primary hypothyroidism is a disease commonly encountered by GPs and internal medicine doctors. It is treated with levothyroxine, the synthetic T4 hormone. If a patient with primary hypothyroidism suddenly requires higher dosages the reason for this should be investigated. Common causes are drug-interactions, pregnancy or non-compliance. Nevertheless, if a patient has other symptoms such as oedema or unexpected weight gain, nephrotic syndrome should be considered. Urinalysis can be very helpful in this. Thyroxin binds to plasma albumin, high levels of which are excreted in patients with nephrotic syndrome. This paper presents two patients, a 45-year-old male and a 72-year-old male, with primary hypothyroidism who due to nephrotic syndrome required large amounts of levothyroxine.