Thyroid RFA is considered a thyroid sparing technique which means nodules are treated but the surrounding thyroid tissue is largely preserved. Despite this changes do occur to thyroid hormone levels which are useful to be aware of.
Immediately following thyroid ablation a mild elevation in thyroid hormones (T3 and T4 hormones) can be expected to occur. This will coincide with a lowering of Thyroid stimulating hormone (TSH) as the body detects a rise in blood thyroid hormone levels and therefore compensates by reducing TSH production. Thyroid hormones are elevated after thyroid RFA because even nodular tissue contains stored T4 as well as some T3 hormone. These hormones are released when the cells are ablated (or destroyed) during the procedure. While hormone levels are elevated this is rarely noticeable to the patient because the rise is mild and short lived. In some cases symptoms of hyperthyroidism can temporarily occur (including palpitations, anxiety and sweats) but this should resolve quickly over a matter of days and medication is rarely necessary.
Over the longer term the vast majority of patients retain normal thyroid function after RFA, with the risk of permanent hypothyroidism (thyroid gland under-activity requiring hormone replacement) less than 1% to 2%. This small risk is in contrast to surgery where a hemithyroidectomy (partial removal of the thyroid gland containing an enlarged nodule) can result in hypothyroidism in 15% to 30% of cases with a frequent need to take lifelong thyroid replacement treatment (levothyroxine).
While the risk of hypothyroidism is low following RFA there are some situations which can increase the risk including treatment of a very large volume of tissue, treating both sides of the gland or if the TSH is already tending towards a hypothyroid state before treatment (the TSH is elevated). Another important factor that increases the risk is underlying inflammation of the gland (thyroiditis) or a condition in which the bodies own immune system is producing proteins which attack the thyroid tissue, called auto-antibodies. Both of these situations means the gland will be functioning less effectively with less reserve and may fail to adjust or compensate to RFA treatment. In the case of inflammation or auto-antibodies the risk of hypothyroidism is difficult to quantify but the need for hormone replacement treatment is still likely to be low (perhaps less than 5%). RFA still preserves function better than surgery. It is also worth remembering that some patients with thyroid inflammation or auto-antibodies in their blood will naturally tend towards hypothyroidism over time, as the gland slowly loses its ability to produce and release thyroid hormone. It is therefore difficult to be certain that thyroid RFA caused, simply hastened or is incidental to thyroid under-activity that develops following treatment.
