Thyroid imbalances have far reaching effects and elicit fatigue, depression, coldness, constipation, poor skin, headaches, PMS, menstrual issues, fluid retention, weight gain, anxiety/panic attacks, decreased memory and concentration, muscle and joint pain, and a low sex drive. GP’s only look at thyroid stimulating hormone (TSH) and this doesn’t always give an accurate picture of the health of your thyroid. This test will tell you whether you have enough T4 (which is made by the thyroid in response to TSH) and T3, which is the form that the body uses. It can also be useful to know how much reverse T3 (rT3) you’re making. Finally, the vast majority of hypothyroidism is autoimmune in origin, and this test will tell you how many anti-thyroid antibodies you have in your bloodstream.
More details and sample report available here.