Assessing thyroid hormone status in a patient with thyroid disease and renal failure: from theory to practice

Hypothyroidism induced severe rhabdomyolysis in a hemodialysis patient

Hypothyroidism occurs relatively common and is a significant cause of morbidity and mortality during the course of chronic kidney disease. Rhabdomyolysis is a potentially life-threatening condition characterised by necrosis of muscular tissue and rarely associates with hypothyroidism. Here we describe a case of rhabdomyolysis due to severe hypothyroidism in a 56-year-old female hemodialysis patient.

The thyroid and the kidney: a complex interplay in health and disease

Thyroid hormones may directly affect the kidney and altered kidney function may also contribute to thyroid disorders. The renal manifestations of thyroid disorders are based on hemodynamic alterations or/and to direct effects of thyroid hormones. The renin-angiotensin system plays a crucial role in the cross-talk between the thyroid and the kidney. Hypothyroidism may be accompanied by an increase of serum creatinine and reduction of glomerular filtration rate (GFR), whereas hyperthyroidism may increase GFR. Treatment of thyroid disorders may lead to normalization of GFR. Primary and subclinical hypothyroidism and low triiodothyronine (T3) syndrome are common features in patients with chronic kidney disease (CKD). In addition low levels of thyroid hormones may predict a higher risk of cardiovascular and overall mortality in patients with end-stage renal disease. The causal nature of this correlation remains uncertain. In this review, special emphasis is given to the thyroid pathophysiology, its impact on kidney function and CKD and the interpretation of laboratorial findings of thyroid dysfunction in CKD.

Thyroid function, cardiovascular events, and mortality in diabetic hemodialysis patients

BACKGROUND

In dialysis patients, the prevalence of thyroid disorders and their impact on specific cardiovascular (CV) events and mortality are largely unknown. The aim of the present study was to analyze whether subclinical thyroid disorders were associated with CV events and mortality.

STUDY DESIGN

Prospective multicenter cohort study.

SETTING & PARTICIPANTS

Thyroid status and clinical outcomes were explored in 1,000 diabetic hemodialysis patients from 178 centers in Germany.

PREDICTOR

Thyroid status, defined by the following cutoff values: euthyroidism (thyrotropin [TSH], 0.30-4.0 mIU/L; free triiodothyronine [T3], 2.7-7.6 pmol/L; and free thyroxine [T4], 11.0-24.0 pmol/L), subclinical hyperthyroidism (TSH<0.3 mIU/L and free T3/free T4 within reference ranges), subclinical hypothyroidism (TSH, 4.1-15.0 mIU/L and free T3/free T4 within reference ranges), euthyroid sick syndrome (free T3<2.7 pmol/L and TSH/free T4 low or within reference ranges).

OUTCOMES

During 4 years' follow-up, prespecified adjudicated end points were determined: sudden cardiac death, myocardial infarction, stroke, combined CV events, and overall mortality. Short-term effects within the first 12 months were contrasted to long-term effects (years 2-4).

MEASUREMENTS

TSH, free T3, and free T4 levels at baseline.

RESULTS

Euthyroidism was present in 78.1% of patients; subclinical hyperthyroidism, in 13.7%; and subclinical hypothyroidism, in 1.6%. Euthyroid sick syndrome was exhibited by 5.4% of patients. The adjusted short-term risk of sudden cardiac death was more than doubled (HR, 2.03; 95% CI, 0.94-4.36) in patients with subclinical hyperthyroidism, and similarly for patients with euthyroid sick syndrome (HR, 2.74; 95% CI, 0.94-7.98) compared with patients with euthyroidism. Short-term mortality was increased almost 3-fold for patients with euthyroid sick syndrome (HR, 2.97; 95% CI, 1.66-5.29), but this effect was not seen in the long term. Subclinical hypothyroidism was not associated with CV events or all-cause mortality. Risks of stroke and myocardial infarction were not affected meaningfully by thyroid disorders.

LIMITATIONS

Observational study design.

CONCLUSIONS

Sudden cardiac death may be influenced by subclinical hyperthyroidism and euthyroid sick syndrome in the short term. Furthermore, euthyroid sick syndrome is associated strongly with mortality in hemodialysis patients. Regular assessment of thyroid status may help estimate the cardiac risk of dialysis patients.

The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease

Accelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature.

Correlation of clinical changes with regard to thyroxine replacement therapy in hypothyroid patients: focusing on the change of renal function

Thyroid dysfunction has an important role in renal insufficiency. The aim of the study was to correlate the change of renal function with other clinical factors after thyroxine therapy in hypothyroid patients. A prospective study was designed and 30 hypothyroid patients were included. All study subjects received 0.15-0.2 mg/day thyroxine for 12 weeks. Diastolic blood pressure and serum levels of creatine phosphokinase (CPK) and myoglobulin decreased significantly after thyroxine therapy. Serum creatinine decreased (0.87 ± 0.22 vs. 0.70 ± 0.17 mg/dl, p < 0.001) and estimated glomerular filtration rate (eGFR) increased significantly (82.06 ± 31.08 vs. 100.31 ± 31.79 ml/min/1.73 m(2); p < 0.001) after thyroxine replacement. Left ventricular ejection fraction (LVEF) was significantly increased after thyroxine replacement (64.47 ± 11.94 vs. 72.40 ± 13.89%, p = 0.026). No significant vascular functional changes of peripheral (pulse wave velocity) and renal interlobar arteries (pulsatility index and resistance index) were noted. The change of eGFR significantly correlated with the changes of serum-free T(4) (fT(4)), CPK, myoglobulin and LVEF. The correlation between the change of eGFR and thyroid-stimulating hormone (TSH) level was not significant. In conclusion, the GFR of hypothyroid patients increased significantly after thyroxine replacement. The change of GFR was significantly correlated with the changes of fT(4), CPK, myoglobulin and LVEF, but not with TSH.

Thyroid hormone action in chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease is characterized by multiple abnormalities in the thyroid hormone physiology. In the present review, we will briefly discuss the effects of uremia on thyroid hormone synthesis, metabolism, transport, and action.

RECENT FINDINGS

Uremic toxins have been shown to interfere at various levels of the thyroid hormone action, including thyroid hormone transport across plasma membrane and thyroid hormone receptor activity. These abnormalities could explain the resistance to thyroid hormone action in uremia, at least in some tissues.

SUMMARY

The pathogenesis of thyroid axis abnormalities in uremia is incompletely understood, and its clinical significance remains unclear. The increasing prevalence of chronic kidney disease underscores the need for further efforts to understand the metabolic consequences of uremia and address questions such as the impact of thyroid hormone therapy.