Hyperthyroidism can present in different forms, and in this country is most often due to a condition known as Grave's Disease. Grave's causes 60-80% of the cases of hyperthyroidism, and is often diagnosed in women in their 20s and 30s. Less common causes include toxic multinodular goiter
(more common in areas with iodine deficiency), subacute thyroiditis, and a hyperfunctioning thyroid nodule.
If you are having symptoms of goiter, tremor and insomnia
in the setting of a low TSH, then I would suspect that your thyroid is the cause, and some form of treatment should be considered. You should also have had further testing done, including measurement of thyroid hormone in the blood (eg free T4) and possibly anti-TPO antibodies (usually very high in Grave's Disease). If the cause of your low TSH was unclear, then you can have thyroid nuclear uptake scans done to help figure out the cause.
If your doctors
do not want to definitely treat your thyroid disease (with curative therapy such as radioactive iodine or surgical removal of the thyroid), then there are other medical options. This includes the use of beta-blockers to help suppress your symptoms, as well as medications to help prevent the formation of new thyroid hormone (methimazole or propylthiouracil).