TSH is like a messenger, it knocks on the door of the thyroid, telling your thyroid to produce more or less of the required thyroid hormones. If you are healthy, the message is determined by your blood levels, and if you have too little thyroid hormone to meet the demands of your body, then TSH knocks on the thyroid door and more hormone is produced or too much and TSH doesn’t knock as often and less hormone is produced.
However, when the thyroid gland is not functioning correctly, theoretically the TSH knocks and knocks on the door to no avail, the thyroid gland is unable to respond and the required hormones are not produced/released. When this happens your TSH blood level will be high.
However, based on normal medical training, a doctor will interpret your results as completely normal if your TSH is within the healthy range. In Australia the “healthy range” for TSH blood levels is ( 0.5 -4.0mIU/L). The problem is with the “healthy range” – a TSH level of 1 to 1.5mIU/L is better for optimum health (provided you are not on any thyroid medication – as optimum levels vary dependent upon you type of medication). My TSH was 3.86 and I was told I was absolutely fine despite a raft of clinical symptoms!