Background Tyroidal disfunction has been widely related with autoimmune diseases and its prevalence is higher (23%) than the one described in normal population (10%). Tyroidal function tests are a common procedure in our rheumatological daily activity but protocols must be performed to detect cases at early onset.

Objectives Screening tyroid tests and its diagnostic value in a Rheumatology Unit.

Methods Between January and December (1998) 10.992 outpatients were visited in our Rheumatology Unit (range of age:18–91). Among them 602 tyroid function tests were performed (5.5%). Treatment with drugs that could interfere tyroidal function were also considered.

Results A higher frequency of tyroid disfunction was observerd in hospitalised patients (31%) than in outpatients (13%)(p < 0.05). The majority of new cases (14%;IC95:11–17%) were subclinical (12.5%;IC95:10–16%) and no significant differences were seen between groups of age (59) and sex. New cases described according to diagnostic: see Table 1 (RA: Rheumatoid Arthritis, SS: Sjögre Syndrom, Arth: Arthritis, Scl: Scleroderma, LES: Systemic Lupus Erythematosus, FM; Fybromialgia, OA: Osteoarthritis, Artg: Arthralgia, Mig: Mialgia, T. Disf: Tyroidal disfunction).

Conclusion These results confirm that the study for tyroidal autoimmunity should be performed to clarify diagnosis, treatment and prognosis of this group of rheumatic patients due to its higher prevalence than in general population.