BACKGROUND
The kidneys are very important in cleaning the blood of toxins. Patients with declining kidney function (chronic kidney disease, CKD) may have to go on dialysis to help cleanse the blood when their kidneys no longer work on their own. Dialysis can be done in different ways, depending on the individual’s condition and other factors. Hemodialysis is when the patient’s blood is run through a machine to help cleanse it several times a week and peritoneal dialysis is when a bag of fluid is inserted into the abdomen then drained several times a day are two different types of dialysis. In general, CKD is a very serious condition, as once a patient goes on dialysis, they are have an increased risk of dying.

Individuals with CKD have a greater risk of an underactive thyroid gland (hypothyroidism) for reasons that are not clear. Having abnormal thyroid function like hypothyroidism or hyperthyroidism (an overactive thyroid gland) is itself associated with higher risks of death, perhaps as a result of heart disease, which has been shown both in the general population with normal kidney function and in those receiving hemodialysis. What is not known is whether having abnormal thyroid function is also associated with higher risks of death in those receiving peritoneal dialysis. This study was done to examine this question using data from a large U.S. national dialysis organization.

THE FULL ARTICLE TITLE:
Rhee CM et al. Thyroid Functional Disease and Mortality in a National Peritoneal Dialysis Cohort. J Clin Endocrinol Metab. 2016 Nov;101(11):4054-4061.

SUMMARY OF THE STUDY
This was a study of 1,484 adults receiving peritoneal dialysis between 2007–2011. Among this group, the researchers looked at the relationships between TSH levels and death from any cause. Patient with a low TSH were considered to be hyperthyroid while those with an increased TSH were considered to be hypothyroid. The patients in this study were primarily women (52%) and non-Hispanic whites (67%) with an average age of 60 years.

The average TSH in this group was slightly increased, with an average serum TSH of 5. Overall, 7% of patients had a low TSH and were considered hyperthyroid and 18% had an increased TSH and were considered hypothyroid. Both groups had increased rates of death. Those with the more severe hyperthyroidism and hypothyroidism had at highest risks of death. Hyperthyroidism and hypothyroidism in this study was defined by blood TSH results alone, with those patients with an undetectable TSH have a 2-fold increased risk of death and those with a TSH >10 having a 3-fold increased risk of death.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that abnormal thyroid function, either hyperthyroidism or hypothyroidism, carries an increased risk of death in patients with CKD receiving peritoneal dialysis. The findings support those of similar studies done in patients receiving hemodialysis and even in those in the general population. The size of the study is large and thus represents its major strength. Overall, little is known regarding this topic, even though both thyroid dysfunction and CKD are relatively common conditions. Future research will help determine whether treatment of the thyroid dysfunction and normalization of TSH levels decreases the risk of death and will also help determine if there is a specific goal of what the TSH levels should be in patients with CKD.

— Angela M. Leung, MD, MSc

ATA THYROID BROCHURE LINKS

Hypothyroidism: http://www.thyroid.org/ hypothyroidism/

Hyperthyroidism: http://www.thyroid.org/ hyperthyroidism/

Thyroid Function Tests: http://www.thyroid.org/ thyroid-function-tests/

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