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Context The impact of abnormal thyroid hormone levels on the cardiovascular system has been explored for decades. Recent emerging evidence suggests that subclinical thyroid dysfunction, especially subclinical hypothyroidism (SCH), significantly affects cardiac indices. Objective We aimed to determine whether levothyroxine (LT4), commonly used to treat hypothyroidism, affects cardiovascular indices in SCH patients. Methods This is a systematic review and meta-analysis. We searched online databases for studies analyzing cardiac morphology and functional changes in SCH patients before and after LT4 supplementation. A total of 294 SCH patients participated and finished the follow-up. The standard mean difference and 95% CI were calculated in fixed or random-effects models. The clinical outcomes analyzed in this study included 18 indicators, mainly covering cardiac morphology, myocardial performance (including various indicators of systolic and diastolic function), mitral wave flow, and systemic vascular resistance. Results A total of 11 studies met our search criteria. All studies explicitly mentioned that serum thyrotropin levels decreased to normal at follow-up. Our results suggest that the cardiac output (CO), left ventricular ejection fraction (LVEF), and the ratio of peak E velocity/peak A velocity were all significantly increased after LT4 supplementation compared with the baseline level. However, we found no clear evidence of significant morphological changes in the heart. Conclusion Judging from the obvious changes in the CO, LVEF, and E/A ratio, LT4 supplementation can effectively improve the cardiac systolic and diastolic dysfunction prevalent in SCH patients. This study provides evidence of the recommendation for LT4 supplementation in adult SCH patients.

Revised Universal Soil Loss Equation (RUSLE) associated with GIS/RS technology has been widely applied to estimate regional soil loss around the world. However, In the Buyuan river basin, the largest tributary within the Upper Mekong, little work has been conducted to assess the situation of soil erosion, though it plays considerable roles for sediment supply to the Lower Mekong after cascade dams have been built in the mainstream of upper Mekong. This work employed RUSLE with GIS/RS to investigate soil erosion in the Buyuan basin during 1989–1999. Results indicate that the total area of soil erosion is larger, accounting for 90% of the total catchment area; annual average erosion modulus of 1989 is 19.996 (t / (km2 · a)), and 17.364 (t / (km2 · a)) in 1999; soil erosion load is about 1.53 × 107 t and 1.33 × 107 t in 1989 and 1999 respectively; According to the Standards for classification and gradation of soil erosion in China, slight and light erosions occupy most area of the basin and increase by 193.99 km2 and 0.22×106 t from 1989 to 1999. During the period, On the contrary, the other classifications (i.e. medium, strong, extremely strong and acute) of erosion reduce by 193.99 km2 and 2.24×106 t respectively. Generally, the situation of soil erosion in this tributary basin was becoming better due to effective contemporaneous the soil and water conservation measures.