AS can cause mild thyroidal impairment.
AS in general lower TBG which leads to lower total T3 & T4...
Free T4 & T3 are usually not affected.. the effect is reversible, it takes a few weeks for TBG to retun to baseline value
Ingestion of Androgenic-Anabolic Steroids Induces Mild Thyroidal Impairment in Male Body Builders
ROMAN DEYSSIG AND MICHAEL WEISSEL
Third Medical University Clinic and L. Boltzmann Institute for Nuclear Medicine, A-1090 Vienna, Austria
..."We conclude that the results of our study show that high doses of androgenic-anabolic steroids, as are used by some athletes, may impair thyroid function to an extent that is not clinically detectable and probably not relevant..."
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