Parathyroidectomy thyroiditis and thyrotoxicosis

Issue: August 2010

ByStephanie L. Lee, MD, PhD, ECNU

ByDaniel J. Rubin, MD

A 60-year-old woman with no history of thyroid disease presented with tachycardia, hypertension and palpitations 11 days after undergoing a difficult resection of a 340 mg right parathyroid adenoma for primary hyperparathyroidism.

Physical exam revealed a heart rate of 120; blood pressure 175/91 mm Hg; a palpable but non-tender thyroid of normal size; a mild tremor; and no Gravesâ€™ ophthalmopathy. The neck incision was healing well with no erythema, edema, heat or discharge.

Daniel J. Rubin

Stephanie L. Lee

Preoperative testing showed a thyroid-stimulating hormone 1.90 uIU/mL (NL 0.35-5.50), calcium 10.4 mg/dL (NL 8.4-10.2) and intact parathyroid hormone 267 pg/mL (NL 11-80). Preoperative parathyroid nuclear scan obtained 5 minutes (early) and 2 hours (late) after the injection of technetium 99m sestamibi demonstrated a uniform trapping of agent within the thyroid with a single more intense rounded focus in the right upper thyroid bed on early images (figure 1A). Delayed images demonstrated persistent trapping of the sestamibi in the right upper thyroid bed focus consistent with a parathyroid adenoma (figure 1B). On the same day, a technetium 99m pertechnetate thyroid scan was performed that showed uniform uptake in the thyroid gland confirming that the delayed isotope trapping on the delayed images of the parathyroid scan was from a parathyroid adenoma (figure 2A). The removal of the parathyroid adenoma was difficult because of its location adjacent to the recurrent laryngeal nerve and the ligament of Berry, requiring extensive manipulation of the right thyroid lobe during the surgery.

On presentation to the ED on postoperative day 11, her laboratory testing showed a TSH of less than 0.01 uIU/mL; triiodothyronine 269 ng/mL (NL 60-181); thyroxine 9.6 mcg/dL (NL 4.5-10.9); and free T₄ index 4.1 (NL 1.0-4.0). Thyroid peroxidase antibodies were negative. Nuclear thyroid scan on postoperative day 15 showed a 4-hour I-123 uptake of 1.8% (NL 5-15%) with reduced visualization of the right lobe, ipsilateral to the surgery (figure 2B), compared with the normal preoperative nuclear thyroid scan (figure 2A). The patient was treated only with a beta-blocker and symptoms resolved within days.

On postoperative day 21, thyroid tests were still mildly elevated with TSH 0.02 uIU/mL; T₃ 169 ng/mL; and free T₄ 1.11 mcg/dL (NL 0.89-1.80). By postoperative week 9, the thyroid tests normalized to baseline with TSH 1.55 uIU/mL and free T₄ 1.05 mcg/dL. The time course of her thyroid function is shown in figure 2.

Postparathyroidectomy thyroiditis was first reported in 1992 by Lewis Braverman, MD, who reported patients seen 2 weeks after surgery with thyrotoxicosis and low radioactive iodine thyroid uptake.

Figure 1. CT scan of the neck with contrast.
Figure 1. Nuclear parathyroid scintigraphy: A. Early images obtained 5 minutes after injection of technetium 99m sestamibi showing uniform trapping in the thyroid gland with a rounded area of increased isotope in the right upper thyroid bed (red arrow). B. Late images obtained 2 hours after the injection showing washout of the isotope from the thyroid and persistent of the isotope in the parathyroid adenoma. Blue arrow: Sternal notch marker.

Photos courtesy of: Stephanie L. Lee, MD, PhD

Figure 2. Barium swallow.
Figure 2. Nuclear thyroid scintigraphy. A. Preoperative technetium 99m pertechnetate thyroid scan showing normal thyroid size and isotope trapping. No cold or hot nodules seen. B. Postoperative I-123 thyroid scan and uptake. Four uptake very low at 1.8% with very little iodine uptake into the right lobe of the thyroid after right upper parathyroidectomy. Arrow: Sternal notch marker.

Figure 2. Barium swallow.
Figure 3. Time course of TSH after parathyroidectomy thyroiditis.

A 2010 review of the subject was recently published by Espiritu and Dean. Prospective studies by Stang and colleagues demonstrated that parathyroidectomy-induced thyroiditis and thyrotoxicosis is a common event, showing that 58 (29%) of 199 patients with normal preoperative TSH levels had a low postoperative TSH between days 7 and 21. About half of these patients with a low TSH were symptomatic, but only five (4%) required beta-blocker treatment. All but one of the patients normalized their thyroid function by 12 weeks; the patient who did not required antithyroid medication for 37 weeks.

Predictors of postparathyroidectomy thyroiditis are having the procedure done in a community vs. academic setting; bilateral vs. unilateral exploration; lithium use; and the absence of a concurrent thyroid lobectomy. Similar cases have been reported in the setting of surgery for secondary and tertiary hyperparathyroidism. The present case is notable for a nuclear thyroid scan that localized very low uptake to the operative site.

Postparathyroidectomy thyroiditis is a commonly under-recognized consequence of parathyroid adenoma resection. The elevated level of thyroid hormone is likely a result of the manipulation of the adjacent thyroid lobe and should be considered an extreme case of palpation thyroiditis. The release of preformed thyroid hormone associated with a low radioactive iodine uptake â€” as in this case â€” results in thyrotoxicosis and not new thyroid hormone synthesis or hyperthyroidism.

Endocrinologists should be aware of the risk for thyrotoxicosis after difficult parathyroid dissection, as the treatment is supportive with beta-blocker therapy and not by a reduction in thyroid hormone synthesis with antithyroid medications such as methimazole or propylthiouracil. In postparathyroidectomy patients at risk for complications of thyrotoxicosis, such as after a difficult exploration and thyroid manipulation, short-term postoperative monitoring of thyroid function and prophylactic beta-blocker therapy should be considered.

Daniel J. Rubin MD, is a fellow in endocrinology, and Stephanie L. Lee, MD, PhD, is associate chief and associate professor of medicine, both in the section of endocrinology, diabetes and nutrition at Boston Medical Center.

For more information:

Braverman LE. Am J Med. 2000;108:519-520.

Espiritu RP. Endocr Pract. 2010;3:1-10.

Stang MT. Surgery. 2005;138:1058-1065.

Walfish PG. J Clin Endocrinol Metab. 1992;75:224-227.