The absolute baseline, and often the only, test needed for monitoring stable thyroid maintenance regimes. If your Thyroid Stimulating Hormone (TSH) level is in the lower reaches of the normal range while you are taking thyroxine replacement, and you have no symptoms, it is likely that all is well and no further testing is required. A high level of TSH generally means an underactive thyroid gland (or under-replacement with thyroxine), while a low level implies an overactive thyroid gland (or over-replacement with thyroxine). TSH (thyroid stimulating hormone) is a hormone manufactured in the pituitary gland (found in the brain). It s role is to stimulate thyroxine production in the thyroid gland (found in the neck). A high level within a health screening is associated with an underactive thyroid gland (hypothyroidism) and a low level is found if the thyroid gland is over-active (hyperthyroidism). Changes in the TSH level alone can indicate underlying thyroid problems even if the thyroxine levels are normal. Free Triiodothyronine (Free T3 or FT3) is the active form of thyroid hormone in our body - this is the actual hormone that does the work at the cellular level. Although not always needed for monitoring thyroid treatment regimes, many specialists advise testing the level of FT3 particularly if the treatment regime is less conventional. Free T4 (FT4 or free thyroxine) is often used in conjunction with TSH to assess thyroid function at a basic level. It is the active form of thyroxine, released from the thyroid gland in the neck. Thyroxine's role is to control metabolism - release of energy from all cells of the body. A lack of thyroxine leads to symptoms which include tiredness and weight gain, whereas an excess will lead to weight loss, rapid heart rate and anxiety. It is generally believed that the Free T4 level is a reliable indicator of thyroid status - ie whether the gland is over-active (hyperthyroidism) or underactive (hypothyroidism). Turnaround: 1 business day
