TSH. When a doctor orders a blood test to look at the thyroid and its function, they might order a tsh, which stands for thyroid stimulating hormone. You can also look at T3 (liothyronine) and T4 levels, which represent the serum amounts of the products produced by the thyroid and its general activity.
Thyroid abbreviation. Though this doesn't cover everything, some abbreviations for thyroid testing include: tsh, t4, t3, (liothyronine) ft4, ft3.
TSH. Throid stimulating hormone is the one of the common tests for thyroid function, others are free t4, total T4 and t3 (liothyronine).
Unclear question. What is a "bac reading"? It may help if you spell out your concern.