Low to normal TSH with normal T3 and T4

[oz1213]

Around the beginning of January, I started experiencing hives all over my body. It has now been almost 5 months and the hives have not diminished, making them chronic urticaria. Mid-March I got my TSH level tested and it came out to be 0.16 in a range of 0.4-4.3. I also got my free T3 and T4 tested, and those were 3.7 in a range of 2.3-4.2 and 1.18 in a range of 0.73-1.95 respectively. A few weeks back, I got my TSH tested again and it came out to be normal (although in the lower region) at 0.53 in a range of 0.5-4.0. Is it possible that the low TSH was just temporary and my levels are returning to normal? I have been noticing other symptoms of hyperthyroidism for the past couple of months, including fatigue, heat intolerance, irritability, and frequent bowel movements.

[gimel]

it is not the low TSH that is causing your problem.  I can think of a scenario that would possibly fit with your experience.  Hashimoto's thyroiditis is a dysfunction with which the autoimmune system erroneously identifies the thyroid gland as foreign to the body and produces antibodies to attack and eventually destroy the gland.  As this proceeds, sometimes nodules will form on the gland and will leak thyroid hormone faster than normal, causing a hyper phase that can last for  a while before reverting to a hypothyroid phase.    

I suggest that you check out the possibility by testing for TPO ab and if negative, then also test for TG ab.  Those are the tests for the antibodies of Hashimoto's Thyroiditis.  Those antibodies associated with Hashi's have been identified as sometimes causing a rash which is known as Hashi's rash.  You can get info about that and other helpful info if you use the search function above for Hashi's rash.  Another suggestion is to test for selenium and consider supplementing with it.  Selenium has been reported to help dampen the level of antibodies..