Hyperthyroidism in autoimmune non-nodular thyroiditis

I am asked to provide an opinion on the case of a 21 years old woman.
The history lacks in detail and is a bit contradictory. It mentions “Basedow’s hyperthyroidism and Hashimoto’s thyroiditis”. While the nomenclature varies, the two conditions can both cause hyperthyroidism but are distinct. As correctly stated in the ultrasound report, the ultrasound description is consistent with both conditions and cannot distinguish reliably. I will discuss both conditions.

Hashimoto’s thyroiditis is most often associated with hypothyroidism, but it may have a transient short phase of hyperthyroidism early on. Hyperthyroidism from Hashimoto’s thyroiditis does not require treatment other than symptom control (for example with beta-blockers) as it resolves spontaneously over a few weeks. Moreover, since hyperthyroidism in Hashimoto’s thyroiditis is caused by release of previously formed and stored thyroid hormone and not by new production of thyroid hormone, methimazole, which blocks the synthesis of thyroid hormone, will not be effective in this condition. For the same reasons, radioactive iodine would not be recommended in such a case.

Basedow’s disease (Graves’ disease in the English literature) is in contrast caused by ongoing thyroid hormone formation and therefore does not remit spontaneously, at least not in the short term. Because of its mechanism, Basedow’s hyperthyroidism can be corrected with methimazole.

The most direct way to distinguish the two forms is to perform a radioiodine uptake test, but this is not always necessary. For example, if there is evidence of hyperthyroidism lasting longer than 6-8 weeks, in a patient without thyroid nodules, then Basedow’s disease is very likely. Tests for TSH receptor antibodies also indicate Basedow’s disease when positive. Since the patient is on methimazole, I will assume that she has been correctly diagnosed with Basedow’s hyperthyroidism and I will answer her questions consequently.

1) Do you agree with the therapy set out and the suggested one?
There are 3 therapeutic options in Basedow’s disease. Methimazole is an effective way to control hyperthyroidism, while hoping for a remission. Most typically, patients are maintained on the medication for 12-18 months after which the drug is slowly tapered until it can be stopped or until there is evidence of returning hyperthyroidism. A good number of patients (maybe 40%) achieve a durable or permanent remission. Many more though will have to decide whether to resume methimazole or turn to one of the other two options, because of relapsing hyperthyroidism. Methimazole is safe, but it can cause agranulocytosis in up to 1/300 cases. While the phenomenon is reversible with discontinuation of the pill, patients must be instructed on promptly reporting high fever and any symptoms of infection, a sign of possible agranulocytosis. Fatalities are extremely rare, but have been described. In this case, I do not think that the low TSH is necessarily an indication of failure of methimazole and should result in an absolute recommendation for an alternative treatment. Titration of methimazole with verification of compliance is expected to result in control of hyperthyroidism in almost all cases.
The second option is radioiodine, which I will discuss below. The third is surgery: total thyroidectomy. Surgery is effective in treating Graves’ disease, but it is invasive, expensive and requires some 7 to 20 days of recuperation. Specific risks from thyroid surgery include permanent hoarseness (from damage to the recurrent laryngeal nerve with vocal cord paralysis) and hypocalcemia from hypoparathyroidism. These outcomes are rare (<1%) in the hands of experienced surgeons.

2) With regard to this, which could be the side effects of Radioiodine therapy, in particular with regard to fertility?
Radioiodine is effective in treating hyperthyroidism, relatively inexpensive and is done on outpatient basis. It basically achieves the same goal of surgery, without anesthesia, without neck scar and without risks to the vocal cords. Radioiodine is absolutely contraindicated during pregnancy and lactation. One single dose is usually sufficient but occasionally a second treatment becomes necessary. Several studies have shown no significant fertility risks with radioiodine treatment; however we recommend avoidance of pregnancy for six months after the treatment. Some people who have the eye manifestations of Graves’ disease (proptosis, diplopia, eyelid swelling) may have a worsening of their ocular symptoms after radioiodine. For those patients, a brief period of treatment with corticosteroid is often given after the radioiodine treatment. Whether radioiodine can cause the new onset of this condition in patients who don’t have it remains unclear. Some studies suggest so, but this is not the experience of many clinicians using radioiodine regularly, like me. Both radioactive iodine and surgery will result in permanent hypothyroidism, easily corrected with thyroid hormone, a treatment without side effects if well monitored.

3) Any alternative and/or complementary therapies?
I do not know of any other alternative proven to be equally safe and effective. Some studies suggest a benefit of selenium supplements in thyroid autoimmunity, but these studies await confirmation.

4) Do you suggest to carry out further diagnostic medical tests?
From the reports received, it is not clear whether the diagnosis of Basedow’s was based on radioiodine uptake, TSH receptor antibody tests, or duration of hyperthyroidism. If any of those was done and found to be consistent with Basedow’s then, I do not recommend any further tests, other than periodic thyroid function tests, liver function tests, complete blood counts.

5) Prognosis?
Prognosis is excellent, with most patients going on with a normal life expectancy and quality, independently of the treatment modality chosen.