Cerebrospinal fluid proteins in subclinical and overt hypothyroidism

Patients and methods - We analysed cerebrospinal fluid (CSF) albumin and immunoglobulin0 G (IgG) concentrations and psychometric performance in subclinical (n=6) and overt hypothyroidism (n= 9) before and after 6 months with L-thyroxine. Results - In overt hypothyroidism, CSF albumin and IgG concentrations were increased before therapy [mean(SD): 328(156) mg/1 and 69(27) mg/1], but within the reference interval [198(48) mg/1 and 39(11) mg/1], P<0.05, after therapy. In contrast, in subclinical hypothyroidism CSF protein concentrations were within the reference intervals before and after therapy. Psychometric testing indicated an improvement in performance in both groups. Conclusion - The increase in CSF proteins in overt hypothyroidism does not appear to be related to thyroid autoimmune disease per se, since we found no increase in CSF proteins in individuals with subclinical hypothyroidism and presence of thyroid antibodies. The increase might rather be caused by a blood-brain barrier dysfunction related to low thyroid hormone concentrations.