The study aimed to evaluate thyroid function profile as a possible factor influencing weight and body composition variation in new DMPA.

A prospective, non-randomized, comparative study was conducted at the University of Campinas, Brazil. Women aged 18–40 years with a BMI less than 30 kg/m2, regular oral glucose tolerance test, no known diseases, and using no medication, who opted to use DMPA were paired by age and BMI with women initiating copper IUD use. The primary outcome measures were thyroid function profile, weight, and body composition, as measured by dual-energy X-ray absorptiometry. We used repeated-measures ANOVA to perform comparisons between times and groups.

We evaluated 28 DMPA users and 24 IUD users who completed the 12-month follow-up. We observed that FT4 levels were higher at 12 months in the DMPA group and that FT4/FT3 ratio had increased in both groups. Additionally, at 12 months, total body mass had grown around 2 kg and lean mass increased in the DMPA group compared to the IUD group; there was also an increase in weight, BMI, total body mass, and fat mass baseline.

The study concluded that no thyroid function changes occurred that could explain the weight increase observed in DMPA users.