Subclinical Hypothyroidism - What is Responsible for its Association with Cardiovascular Disease?

Relationship of subclinical hypothyroidism on epicardial adipose tissue: a systematic review and meta-analysis

Accumulation of epicardial adipose tissue (EAT) and Subclinical hypothyroidism (SH) are associated with increased cardio-metabolic risk. The objective of this study was to quantitatively compare EAT thickening between patients with SH and healthy controls. Therefore, after searching the PubMed/MEDLINE, Embase, Science Direct, Scopus, Google Scholar, and Cochrane databases; we analyzed a group of observational studies who compare the EAT changes between SH vs control groups. A total of 9 studies were included in the final analysis, for a total of 424 patients with SH and 330 controls. Random or fixed effects models were used. Pooled analysis revealed that HS increased EAT (MD: 1.0 mm [0.40; 1.50]; P < 0.01). This meta-analysis suggests that the amount of EAT is significantly increased in SH patients. EAT might be a marker of cardiovascular risk in patients with SH.

Subclinical Hypothyroidism and Incident Depression in Adolescents and Young Adults: Results from a Nationwide Representative Prospective Study

Background: Although the relationship between subclinical hypothyroidism and major depressive disorder (MDD) has been studied in adults in cross-sectional and prospective population-based studies, this has not yet been done in adolescents. However, since thyroid function and MDD risk are subjected to maturational processes and ramifications of illness duration over the life span, these findings may not readily transfer to adolescents. Methods: The relationship between subclinical hypothyroidism and MDD was studied in a representative subsample of the nationwide KIGGS ("The German Health Interview and Examination Survey for Children and Adolescents") survey. A total of 4118 adolescents were examined over a median period of 6 years, and data were analyzed by a logistic regression approach accounting for important covariates related to thyroid function and/or MDD risk. The same approach was chosen to investigate the relationship between quartiles of thyrotropin (TSH) and free thyroxine (fT4) levels and incident MDD in euthyroid participants to broaden the focus on the relationship between thyroid hormone levels and MDD in a dose-response manner. Results: During the observation period, 121 cases of MDD were reported. There was no association between subclinical hypothyroidism and MDD when comparing 111 adolescents with subclinical hypothyroidism with 4007 euthyroid adolescents, representative of ∼106,000 and 3,610,000 adolescents from the general pediatric population, respectively. This also applied when studying the relationship between quartiles of TSH and fT4 levels and MDD in euthyroid participants. All results were confirmed by sensitivity analyses accounting for thyroid autoimmunity. Conclusions: Consistent with findings in adults, there is no association between subclinical hypothyroidism or quartiles of TSH and fT4 levels in the normal range and MDD in adolescents, despite potential age-related differences regarding thyroid function and MDD risk.

Investigation of the effect of boron on thyroid functions and biochemical parameters in hypothyroid induced-rats

In the study investigating the effects of boron on thyroid hormones and some biochemical parameters in hypothyroid rats, 49 Wistar Albino male rats were divided into seven groups; (Control (C), Hypothyroidism (H), boron groups (B10, and B20), hypothyroid + boron groups (HB10 and HB20), and Treatment (T). Four groups (H, HB10, HB20, and T) were administered 10 mg/kg (B10 and HB10), 20 mg/kg (B20 and HB20) boron for 3 weeks, respectively after hypothyroidism was induced using Propycil® containing propylthiouracil (PTU). Thyroid hormone analyses and biochemical measurements were made from the serum and thyroid gland tissue was examined histopathologically. According to the findings, the fT3 level increased in the B10 group compared to the control group (p < 0.05). While AST, ALT, and ALP activities were found to be higher in the hypothyroid group than in the control group, AST and ALP activities in the HB10 and HB20 groups decreased to values close to the control group. Total cholesterol levels were found to be lower in boron-given groups compared to control and hypothyroid groups (p < 0.05). Sodium iodide symporter (NIS) immunoreactivity was found to be high in hypothyroid rat groups. As a result, it was observed that the increased AST and ALP activities in rats decreased with boron administration. The serum hormone levels measured in the study are not sufficient to understand the effect of boron on the thyroid gland, and it was concluded that further studies at the molecular level are needed to understand the effects of boron on the thyroid gland.

Oxidative stress and radioiodine treatment of differentiated thyroid cancer

It is hypothesized that the oxidative stress level in thyroid cancer patients is additionally upregulated by radioactive iodine (RAI) treatment, that may exert an important impact on future health concerns. In our study, we evaluated the oxidative stress level changes using the measurement of malondialdehyde (MDA) concentration in patients with differentiated thyroid cancer (DTC) undergoing RAI treatment. Considering the results obtained in the study group, the serum levels of MDA in DTC patients were significantly higher compared to the healthy subjects (p < 0.05). The MDA concentration was significantly higher on the third day after RAI (p < 0.001) and significantly lower one year after RAI (p < 0.05) in DTC patients compared to the baseline concentration. Moreover, the redox stabilization after RAI treatment in patients with DTC during a year-long observation was demonstrated. Accordingly, an increased oxidative stress impact on the related biochemical parameters reflecting the health conditions of the DTC patients was determined. Our study showed that increased oxidative stress reflected by MDA measurements in DTC patients is further enhanced by RAI, but this effect is no longer observed one year after the therapy.

Subclinical hypothyroidism is independently associated with poor renal outcomes in patients with chronic kidney disease

PURPOSE

It remains unclear whether subclinical hypothyroidism (SCH) is associated with renal prognosis in patients with chronic kidney disease (CKD). Therefore, we prospectively investigated the association of SCH with renal outcomes in CKD.

METHODS

We conducted a prospective observational study of 480 euthyroid patients and 89 patients with SCH. The endpoints were defined as a composite of doubling of serum creatinine (SCr), end-stage renal disease (ESRD), or death, and a composite of doubling of SCr or ESRD was added as an alternative outcome. Logistic regression analyses were used to identify the factors associated with SCH. In addition, a Cox proportional hazards model was performed to determine whether SCH was associated with poor renal outcomes.

RESULTS

During a median follow-up period of 26.1 months, doubling of SCr, ESRD, or death and doubling of SCr or ESRD occurred in 244 and 213 patients, respectively. In univariable logistic regression analyses, SCH was significantly associated with older age, lower hemoglobin, higher proteinuria, lower estimated glomerular filtration rate (eGFR), and higher log B-type natriuretic peptide (BNP). Multivariable Cox analyses showed that SCH was associated with poorer renal outcomes after adjustment for covariates, including eGFR and log BNP [doubling of SCr, ESRD, or death: hazard ratio (HR) 1.61, 95% confidence interval (CI), 1.16-2.23; doubling of SCr or ESRD: HR 1.53, 95% CI 1.07-2.20], compared with euthyroidism.

CONCLUSIONS

In CKD, SCH is independently associated with poor renal outcomes, suggesting that screening for SCH might be needed to accurately predict renal prognosis.