Resistance to human recombinant erythropoietin in hypothyroidism

Thyroid functional disease: an under-recognized cardiovascular risk factor in kidney disease patients

Thyroid functional disease, and in particular hypothyroidism, is highly prevalent among chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. In the general population, hypothyroidism is associated with impaired cardiac contractility, endothelial dysfunction, atherosclerosis and possibly higher cardiovascular mortality. It has been hypothesized that hypothyroidism is an under-recognized, modifiable risk factor for the enormous burden of cardiovascular disease and death in CKD and ESRD, but this has been difficult to test due to the challenge of accurate thyroid functional assessment in uremia. Low thyroid hormone levels (i.e. triiodothyronine) have been associated with adverse cardiovascular sequelae in CKD and ESRD patients, but these metrics are confounded by malnutrition, inflammation and comorbid states, and hence may signify nonthyroidal illness (i.e. thyroid functional test derangements associated with underlying ill health in the absence of thyroid pathology). Thyrotropin is considered a sensitive and specific thyroid function measure that may more accurately classify hypothyroidism, but few studies have examined the clinical significance of thyrotropin-defined hypothyroidism in CKD and ESRD. Of even greater uncertainty are the risks and benefits of thyroid hormone replacement, which bear a narrow therapeutic-to-toxic window and are frequently prescribed to CKD and ESRD patients. In this review, we discuss mechanisms by which hypothyroidism adversely affects cardiovascular health; examine the prognostic implications of hypothyroidism, thyroid hormone alterations and exogenous thyroid hormone replacement in CKD and ESRD; and identify areas of uncertainty related to the interplay between hypothyroidism, cardiovascular disease and kidney disease requiring further investigation.

Impact of thyroid dysfunction on erythropoietin dosage in hemodialysis patients

BACKGROUND

Although thyroid diseases exist in patients with renal failure, thyroid function tests are not routine tests in patients on chronic hemodialysis (HD). Therefore, the impact of thyroid diseases on erythropoietin (EPO) dosage in HD patients is not well defined. This study evaluated the relationship between the dose of EPO and the presence or absence of thyroid dysfunction in HD patients.

METHODS

This study included 1013 adult patients on HD who did not have a malignancy, liver cirrhosis, thalassemia, iron deficiency, gastrointestinal bleeding, or a major operation within 6 months. Patients were characterized as being euthyroid, or having the sick euthyroid syndrome, primary hypothyroidism, subclinical hypothyroidism, hyperthyroidism, or subclinical hyperthyroidism based on thyroid function tests. Routine biochemistry profiles including an index of the efficiency of HD, along with clinical data over the previous 6-month period, were collected and analyzed. Multiple regression models were employed to assess the relationship between the dose of EPO and the presence or absence of thyroid status.

RESULTS

The mean monthly EPO dosages were 77.7±37.0, 70.2±40.6, 90.8±68.4, 78.5±46.7, and 82.3±41.2 μg, respectively, in the sick euthyroid syndrome, euthyroid patients, hypothyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism groups (p<0.05). After adjustment of all other variables in multiple regression, the mean monthly EPO dosage was 19.00±8.59 μg more in hypothyroid patients compared with euthyroid patients (p=0.027). Further, considering an interaction with the presence of diabetes, the mean monthly EPO dosage in patients with either hypothyroidism or subclinical hypothyroidism and diabetes was 54.66±17.12 μg (p=0.001) and 31.51±10.38 μg more than that of euthyroid patients, respectively (p=0.002).

CONCLUSIONS

In HD patients, the EPO dosage required to maintain the target hemoglobin level is significantly higher in patients having both hypothyroidism or subclinical hypothyroidism and diabetes than in euthyroid patients.

Prevalence of clinical and subclinical thyroid disease in a peritoneal dialysis population

AIMS

We investigated dialysis duration, dose of erythropoietin (EPO), and clinical manifestations in peritoneal dialysis (PD) patients with subclinical hypothyroidism.

METHODS

This cross-sectional study, performed in 3 centers, assessed 122 adult patients on PD for more than 6 months with regard to demographic data, dialysis duration, thyroid function, biochemical data, EPO dose, and clinical manifestations. Thyroid dysfunction was determined by serum thyroid-stimulating hormone, free thyroxine, total thyroxine, total triiodothyronine, antithyroid peroxidase antibodies, and auto-antibodies against thyroglobulin.

RESULTS

Of the 122 study patients, 98 (80.3%) were assessed as having euthyroidism; 19 (15.6%), subclinical hypothyroidism; and 5 (4.1%), subclinical hyperthyroidism. The proportion of women (74.2% vs. 57.1%, p = 0.038), the mean duration of PD (58.1 months vs. 37.9 months, p = 0.032), and the weighted mean monthly EPO dose (1.22 μg/kg vs. 1.64 μg/kg, p = 0.009) were significantly higher in the subclinical hypothyroidism group than in the euthyroidism group, but the prevalences of coronary artery disease and cerebrovascular disease were not. From the multivariate model, PD duration was more significant than sex as a risk factor for subclinical hypothyroidism (p = 0.0132).

CONCLUSIONS

Subclinical hypothyroidism is frequent in PD patients, especially female patients and patients with a longer PD duration. Compared with euthyroid patients, patients with subclinical hyperthyroidism need a higher dose of EPO to maintain a stable hemoglobin level.

Thyroid hormone abnormalities and frailty in elderly patients with chronic kidney disease: a hypothesis

Thyroid hormones play a crucial role in the metabolic activities of adults, affecting almost every organ system. All types of thyroid diseases are encountered in the elderly. As symptoms and signs of thyroid diseases may overlap with what is considered to be "normal aging," the presence of a thyroid disorder may go undiagnosed in the elderly. This potential problem is further compounded in elderly patients with chronic kidney disease (CKD), where the presence of an underlying hormonal problem such as hypothyroidism may be erroneously attributed to multiple comorbidities, the aging process, or the kidney disease. Frailty is being recognized as a contributing factor to the poor outcomes (hospitalization and high mortality) in elderly patients with CKD. Predisposing factors leading to frailty in elderly with CKD such as increased inflammatory markers, anemia, low testosterone, sarcopenia, and depression are associated with thyroid hormonal abnormalities. These associations are remarkable and raise the question of whether routine monitoring and screening for thyroid hormone changes in elderly CKD patients might be helpful in identifying reversible causes of frailty. In this review, we will focus on the associations between thyroid hormone abnormalities and the predisposing factors of frailty in elderly patients with CKD. If a cause-effect relationship of thyroid hormone abnormalities and factors predisposing to frailty in CKD patients is established, identification and treatment of thyroid abnormalities in this population would assume increased importance.