- After removing half of the thyroid gland, about one in four people needs hormone afterwards, and after removing the entire gland, everyone does.
- After an ablation, permanent hypothyroidism is rare: below 1 % in the large series.
- There is a higher-risk subgroup, above all people with thyroid antibodies, and it is worth knowing beforehand.
The thyroid makes the hormone that regulates metabolism. If it is removed, it has to be replaced with a tablet every day, and if it is kept and keeps working, it does not. That is the logic of treating a benign nodule without removing the gland. What follows is how much of that logic is backed by the literature, and where it has nuances.
After surgery
When the whole gland is removed, taking hormone is an anatomical consequence, not a failure: no tissue is left to produce it. When half of the gland is removed, a Surgery in which half of the thyroid gland (one lobe) is removed. Also called lobectomy., the remaining half is usually enough, but not always.
- 29 %of people develop hypothyroidism after a hemithyroidectomy, and 23 % need levothyroxine.Cooper D et al. Thyroid Res. 2024, 17: 18. Meta-analysis of 66 studies.
- 100 %after a total thyroidectomy. It is expected, and it is compensated with a daily tablet adjusted by blood tests.Anatomical consequence: without a gland there is no hormone production.
After an ablation
Ablation heats the nodule and leaves the rest of the gland intact. In the Korean multicenter series by Baek, with 1,459 patients treated with radiofrequency, permanent hypothyroidism appeared in a single case, and in the largest published series of thermal ablation, with more than two thousand patients, the overt hypothyroidism seen at one month had disappeared by twelve months, while the An abnormality seen only in blood tests (TSH rises) without the person noticing symptoms. form, detected only in blood tests, was transient in almost every case.
It is worth saying plainly: there is no dedicated meta-analysis yet on hypothyroidism after radiofrequency specifically, nor a direct comparison between radiofrequency and hemithyroidectomy for that outcome. The difference is large and consistent across series, but it is described as «rare», not as «impossible».
The first week: the surprising figure
In the first days after the ablation, blood tests may show the opposite of what is feared: a temporary excess of hormone, because the heated nodule releases what it had stored. It happens in more than a third of patients, almost always without symptoms, and settles on its own. It is worth knowing so as not to be alarmed by a first-week result.
Who is at higher risk
Not everyone starts from the same point. Three factors raise the chance that the gland will not compensate afterwards: having positive Antibodies against a thyroid enzyme. When positive they indicate autoimmune thyroiditis, which can progress to hypothyroidism., a TSH that is already high before the procedure, and ablating a large proportion of the thyroid volume. The Korean guideline records it this way: in patients with thyroid antibodies «it may be prudent to warn them before treatment». That is why thyroid function and antibodies are checked before, not after.
- Positive anti-TPO antibodies or a previous diagnosis of Hashimoto's thyroiditis.
- Elevated baseline TSH, even if you do not yet take hormone.
- Large nodules that occupy a significant part of the gland.
- Li S et al. Changes in thyroid function after thermal ablation of thyroid nodules. Front Endocrinol. 2025, 16: 1557725.
- Cooper D et al. Hypothyroidism after hemithyroidectomy: systematic review and meta-analysis. Thyroid Res. 2024, 17: 18.
- Wang N et al. Int J Hyperthermia. 2021, 38(1): 1060-1068.
- Kim JH et al. 2017 Thyroid Radiofrequency Ablation Guideline: Korean Society of Thyroid Radiology. Korean J Radiol. 2018, 19(4): 632-655.
