A person taking exogenous thyroid hormone in an illegal diet pill would have T3 and T4 and TSH levels while taking the diet pill.

A person taking exogenous thyroid hormone in an illegal diet pill would have more than normal T3 and T4 and less than normal TSH levels while taking the diet pill.

Explanation:

If a person is taking exogenous thyroid hormone in an illegal diet pill, the  T3 and T4 would be higher than usual since the body is receiving the thyroid hormone when it does not need it because it can produce it by itself. The TSH is the Thyroid Stimulating Hormone. This hormone stimulates the production of T3 and T4 in the thyroid gland. As the body receives an external dose of the thyroid hormone, the TSH levels are lower to try and balance the excess of T3and T4.