Medication
Many bodybuilders take thyroid hormone in hopes of increasing their metabolism and reducing their bodyfat percentage for a contest. It is good in theory and generally harmless over a short duration, but in order to lessen the likelihood of muscle catabolism, a blood test in conjunction with use is needed.
A blood test will tell you if you are taking excess thyroid hormone and are hyperthyroid - an undesirable, catabolic condition.
There are three types of medication used to boost circulating thyroid hormone:
T4:
Common names:
Synthroid, Levoxyl, Unithroid, Levothroid, and Euthyrox
T3:
Common names:
Cytomel, Cynomel, Cyronine, Cytomel Tabs, Euthroid, Linomel, Liothyronin, Neo-Tiroimade, Ro-Thyronine, T3, Tertroxin, Thybon, Ti-Tre, Tiromel, Tironina, and Trijodthyronin.
Powdered Thyroid:
Common names:
Armour Thyroid, S-P-T, Thyrar, Thyroid Strong (animal thyroid gland with a set T4/T3 mix).
Based on their experience, physicians generally prescribe either T4 or Powdered Thyroid, but generally not both. Some will prescribe T4 and T3 simultaneously. When a physician prescribes both T3 and T4, the type of abnormal thyroid condition being treated usually dictates it.
Bodybuilders prefer the active hormone, T3, when preparing for a contest because it is the more potent hormone.