Under-Active Thyroid test to measure the TSH level in your blood to identify an underactive thyroid. The test kit is not able to identify an overactive thyroid. The symptoms of an underactive thyroid are often vague and usually develop quite slowly such that you may not notice them. When the body doesn’t have enough thyroid hormone many of the body’s functions slow down. Symptoms of underactive thyroid include: Tiredness Weight Gain Low Mood Being Sensitive To The Cold Dry Skin & Hair Muscle Aches, Weakness and Cramps Constipation Loss of Libido (Sex Drive) Irregular and or Heavy Periods Carpal Tunnel Syndrome