The oversuppression of thyroid-stimulating hormone (TSH) was associated with cognitive disorders in older adults in a recent cohort study. Nevertheless, a commentary in the Journal of Family Medicine and Primary Care advises that TSH oversuppression may be intentional and necessary in patients who have had a total thyroidectomy for cancer.

“Although management of benign thyroid disease is often straightforward, primary care teams must be vigilant in recognizing patients who are on LT4 [levothyroxine] for TSH suppression after total thyroidectomy,” wrote corresponding author Faraz Mughal, MBChB, DCH, and colleagues.

In patients with differentiated thyroid cancer (papillary and follicular carcinoma) who require postoperative radioiodine remnant ablation (RRA), supraphysiological doses of LT4 are used to suppress TSH and decrease the risk of cancer recurrence. If dynamic risk stratification of cancer recurrence risk 9 to 12 months after RRA indicates, TSH suppression may be relaxed.

Primary care clinicians usually monitor patients on LT4 annually with TSH tests, but the commentary advises clinicians to exempt patients with thyroid cancer from routine TSH checks.

“Dose adjustment in this cohort should only be carried out in discussion with their thyroid surgeon or endocrinologist,” the authors advised.

If, in between specialist appointments, patients present to primary care with symptoms of TSH oversuppression or undersuppression, clinicians should order thyroid function tests and inform the patient’s thyroid surgeon or endocrinologist. Undersuppression often occurs when patients take LT4 at the incorrect time of the day. Medications, foods, and nutritional supplements can also affect the absorption and efficacy of LT4.

“Patients should be advised to take LT4 first thing in the morning, 30–60 minutes before taking any other medications, caffeine-containing drinks, or breakfast,” the authors wrote.

Patients with ongoing TSH suppression are usually under the care of a thyroid surgeon for up to a decade. If patients present to primary care because of overt hypothyroidism or complications of oversuppression, such as atrial fibrillation, osteoporosis, irritability, insomnia, and hypomania, timely referral to an endocrinologist is warranted.

“Urgent referrals to specialists may be needed to manage potential complications of under and oversuppression,” the authors explained, “as well as potential cancer recurrence.”