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..."
Feldman EB, Carter AC. 1960 Endocrinologic and metabolic effects of 17-alpha-methyl-19-nortestosterone in women.
J Clin Endocrinol Metab. 20:842-857
Keitel H, Sherer MG. 1957 Marked depression of the plasma protein-bound iodine concentration in the absence of clinical hypothyroidism during testosterone medication.
J Clin Endocrinol Metab. 17~854-861.
Federman DD, Robbins J, Rall JE. 1958 Effects of methyl testosterone on thyroid function, thyroxine metabolism and thyroxine binding protein.
J Clin Invest. 37:1024-1030.
Kochakian CD, Evans WW. 1956 The iodine metabolism of the thyroid of androgen treated rats.
Engbring NH, Engstrom WW. 1959 Effects of estrogen and testosterone on circulating thyroid hormone.
J Clin Endocrinol Metab. 19:783-796.
Alin M, Rahkila P, Rein&i M, Vihko R. 1987 Androgenic-anabolic
steroid effects on serum thyroid, pituitary and steroid hormones in
athletes. Am J Sports Med. 15:357-361.