LAUSR

Subclinical hypothyroidism (SCH) is a common condition in adults, especially in women. Although not considered by current guidelines in the treatment decision of SCH [1–5], concern exists regarding the association with decreased glomerular filtration rate (GFR). However, in the absence of overt hypothyroidism (TSH >20 mIU/L or low T4), TSH elevation might be a consequence of decreased GFR and does not reflect true thyroid dysfunction [1, 6]. Although SCH has a negative impact on GFR, this has been suggested particularly in patients with established kidney disease [7– 12] or associated conditions that are also known to compromise renal function, such as diabetes mellitus and arterial hypertension [7, 8, 10, 13]. The repercussion of SCH on GFR in adults without known kidney disease or risk conditions for renal dysfunction is less studied [14]. A reasonable consensus on the need for treatment exists for individuals with SCH and TSH >10 mIU/L, except for those older than 70 years who are asymptomatic [1–5]. In contrast, L-T4 therapy in SCH and TSH up to 10 mIU/L is still controversial. This observation, together with the fact that individuals with TSH up to 10 mIU/L account for approximately 80% of cases of SCH [4, 5], renders this group interesting for study. To evaluate the relationship between SCH with TSH ≤10 mIU/L and decreased GFR, this study compared the estimated GFR (eGFR) between adult women (age ≤65 years) without known renal disease or risk factors, measured at diagnosis and after 5 years of persistent SCH, and euthyroid. Since the duration of thyroid dysfunction is important for the occurrence of eventual repercussions [1], evaluation after 5 years of untreated SCH was included in addition to the measurement at diagnosis.