# Cross-section of thyroidology and nephrology: Literature review and key points for clinicians

## TL;DR

This paper reviews how thyroid and kidney diseases interact and provides key clinical guidelines for managing patients with both conditions.

## Contribution

The paper highlights novel clinical insights on thyroid function in CKD and ESRD patients and treatment considerations for thyroid disorders.

## Key findings

- Euthyroid patients with CKD may have altered thyroid hormone levels that are physiologically normal.
- Levothyroxine supplementation in CKD patients can delay renal failure progression.
- Radioiodine therapy in ESRD patients requires careful dosing due to prolonged radiation risk.

## Abstract

There are several key points clinicians should consider when managing patients with overlapping thyroid and renal disease. Patients who are euthyroid and have chronic kidney disease (CKD) may physiologically have normal-high thyroid stimulating hormone (TSH), low free thyroxine (FT4), low free triiodothyronine (FT3) and normal-low reverse triiodothyronine (rT3). Untreated subclinical and primary hypothyroidism among patients with (CKD) is associated with reversible progression of renal failure. Supplementing these (CKD) patientswith levothyroxine can delay the progression of renal failure and prevent end stage renal disease (ESRD). Untreated hyperthyroidism increases the glomerular filtration rate (GFR) by 18 to 25%. Thus, the management of hyperthyroidism may unmask patients with undiagnosed CKD. There is no dosage adjustment required for methimazole among patients with CKD. However, methimazole may be eliminated during hemodialysis (HD) by around 30 to 40%. Patients with papillary thyroid cancer and ESRD may have higher rates of aggressive characteristics. Patients with CKD and ESRD undergoing radioiodine I-131 treatment for thyroid cancer are at increased risk of prolonged radiation transmission risk due to decreased iodine urinary excretion. Additionally, the optimal dosing and timing of radioiodine I-131 therapy amongst patients with ESRD and thyroid cancer requires further research. The use dosimetry studies and multidisciplinary coordination among nuclear medicine, nephrology and endocrinology is recommended for these patients.