Variations of sex hormone-binding globulin in thyroid dysfunction

With the aim of understanding the variations of the levels of sex hormone-binding globulin (SHBG) in thyroid dysfunction, we studied the influence of factors that also modify SHBG, such as menopausal status, age, and body mass index (BMI) in women with hypothyroidism and hyperthyroidism, both overt and subclinical. Statistical analysis was performed by means of analysis of variance (ANOVA), stepwise multiple regression, and partial correlation. The ANOVA showed a significant statistical difference among the means of SHBG of all groups (p<0.01). The difference was due to the group that included hyperthyroid women. Multiple regression analysis showed that the main factors influencing SHBG were BMI and age, except for the hyperthyroid group, where the most important independent variables were triiodothyronine (T3) and thyroxine (T4). Partial correlation controlling the effect of BMI and age showed no association between SHBG and the other variables in all groups except for the subclinical hyperthyroid and hyperthyroid, where we found a significant association between SHBG and T4 and T3. The premenopausal or postmenopausal status did not modify SHBG levels. When the patients are taken as a whole, BMI, age, T4, and T3 all have an association with SHBG levels according to the multiple regression analysis.