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. 2024 Sep 10:17:11795514241278519.
doi: 10.1177/11795514241278519. eCollection 2024.

Serum Potassium in Thyroid Cancer Patients With Hypothyroidism During Thyroid Hormone Withdrawal: A Retrospective Study

Poonyisa Tangsermvong  1 , Wichana Chamroonrat  2 , Siripong Vittayachokkitikhun  2 , Chutintorn Sriphrapradang  1
Affiliations

Serum Potassium in Thyroid Cancer Patients With Hypothyroidism During Thyroid Hormone Withdrawal: A Retrospective Study

Poonyisa Tangsermvong et al. Clin Med Insights Endocrinol Diabetes. .

Abstract

Background: Several case reports and a few studies have reported that hypothyroid patients have elevated serum potassium levels. However, hypothyroidism has not been widely accepted as a cause of hyperkalemia.

Objectives: This study aims to evaluate the incidence of hyperkalemia and factors influencing serum potassium levels in thyroid cancer patients with hypothyroidism during thyroid hormone withdrawal before radioactive iodine (RAI) treatment.

Methods: We conducted a retrospective review of electronic medical records from January 2017 to June 2021, involving 956 thyroid cancer patients post-thyroidectomy and undergoing RAI. Laboratory parameters, including serum potassium levels, were collected in both euthyroid (<1 year prior to RAI) and hypothyroid states.

Results: Among 508 patients (mean age 52 years, 79.3% female), hyperkalemia (potassium ⩾ 5.0 mEq/L) occurred in 2.8%, without severe hyperkalemia (potassium ⩾ 6.5 mEq/L). The hypothyroid state exhibited significantly higher serum potassium than the euthyroid state [4.16 (IQR, 3.94-4.41) vs 4.10 (IQR, 3.90-4.35) mEq/L, P < .01]. The mean change in potassium levels between the euthyroid and hypothyroid state was 0.05 ± 0.17 mEq/L. Pre-thyroid hormone withdrawal (euthyroid state) factors associated with serum potassium levels in the hypothyroid state included age, use of angiotensin-converting enzyme inhibitors, diabetes mellitus, serum BUN/creatinine, serum potassium levels, hemoglobin A1c (positive correlation); and thiazide use and eGFR (negative correlation). In the hypothyroid state, hyperkalemia was more likely in patients with serum potassium ⩾4.2 mEq/L (OR 9.36, P < .01) or free T4 ⩾1.38 ng/dL (OR 7.05, P < .01) during the euthyroid state.

Conclusions: The incidence of hyperkalemia was low in our hypothyroid cohorts. However, physicians should remain vigilant for cases with risk factors for developing hyperkalemia.

Keywords: Electrolyte; hyperkalemia; hypothyroidism; iodine radioisotopes; thyroid neoplasms; water-electrolyte imbalance.

Plain language summary

Serum Potassium in Hypothyroid Patients A retrospective cohort study of thyroid cancer patients undergoing radioactive iodine therapy found a low incidence of hyperkalemia (2.8%) during hypothyroidism. Patients exhibited higher serum potassium levels, influenced by factors included age, medication use (ACEI), diabetes mellitus, and initial potassium levels. Elevated initial potassium and thyroid hormone levels were associated with higher risk of hypothyroid-related hyperkalemia. Physicians should remain vigilant for hyperkalemia in these patients, particularly those with predisposing factors, warranting further mechanistic studies and broader validations.

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Conflict of interest statement

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
The standard protocol of thyroid hormone withdrawal for thyroid cancer patients who have undergone radioactive iodine therapy at our hospital. Abbreviations: LT4, levothyroxine; RAI, radioactive iodine.
Figure 2.
Figure 2.
Flow of study participants. Abbreviations: CKD, chronic kidney disease; DM, diabetes mellitus; HbA1c, hemoglobin A1c.
Figure 3.
Figure 3.
ROC of serum potassium (A) and free T4 levels (B) predicting the development of hyperkalemia during hypothyroidism.
See this image and copyright information in PMC

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