***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE The role of thyroxine replacement in sub clinical hypothyroidism remains unclear . We performed a 6-month r and omized , double-blind , placebo-controlled trial to evaluate the effects of thyroxine treatment for mild sub clinical hypothyroidism , defined as a serum thyroid-stimulating hormone level between 5 to 10 microU/mL with a normal serum free thyroxine level ( 0.8 - 16 ng/dL ) . SUBJECTS AND METHODS We r and omly assigned 40 women with mild sub clinical hypothyroidism who had presented to their family practitioners to either thyroxine treatment ( n = 23 ; 50 to 100 microg daily ) or placebo ( n = 17 ) .  Health-related quality of life ( Hospital Anxiety and Depression scale , 30-item General Health Question naire ) , fasting lipid profiles , body weight , and resting energy expenditure were measured at baseline and 6 months . RESULTS The most common presenting symptoms were fatigue ( n = 33 [ 83 % ] ) and weight gain ( n = 32 [ 80 % ] ) . At presentation , 20 women ( 50 % ) had elevated anxiety scores and 22 ( 56 % ) had elevated scores on the General Health Question naire .  Thirty-five women completed the study . There were no significant differences in the changes from baseline to 6 months between women in the thyroxine group and the placebo group for any of the metabolic , lipid , or anthropometric variables measured , expressed as the mean change in the thyroxine group minus the mean change in the placebo group : body mass index , -0.3 kg/m(2 ) ( 95 % confidence interval [ CI ] : -0.9 to 0.4 kg/m(2 ) ) ; resting energy expenditure , -0.2 kcal/kg/24 h ( 95 % CI : -1.3 to 1.0 kcal/kg/24 h ) ; and low-density lipoprotein cholesterol , -4 mg/dL ( 95 % CI : -23 to 15 mg/dL ) . There was a significant worsening in anxiety scores in the thyroxine group ( scores increased in 8 of 20 women and were unchanged in 2 of 20 ) compared with the placebo group ( scores increased in 1 of 14 women and were unchanged in 6 of 14 ; P = 0.03 ) . CONCLUSIONS ; We observed no clinical ly relevant benefits from 6 months of thyroxine treatment in women with mild sub clinical hypothyroidism Sub clinical hypothyroidism ( sHT ) affects 5 - 15 % of the general population ; however , the need of lifelong L-T(4 ) therapy is still controversial . As myocardium is a main target of thyroid hormone action , we investigated whether sHT induces cardiovascular alterations .  Twenty sHT patients were r and omly assigned to receive placebo or L-T(4 ) therapy  and were followed for 1 yr . Twenty sex- and age-matched normal subjects served as controls .  Doppler echocardiography and videodensitometric analysis  were performed in all subjects . Myocardium textural parameters were obtained as mean gray levels , which were then used to calculate the cyclic variation index ( CVI ; percent systolic/diastolic change in mean gray levels ) . Patients had a significantly higher isovolumic relaxation time ( 3.1 + /- 0.5 vs. 2.6 + /- 0.6 ; P < 0.03 ) , peak A ( 0.77 + /- 0.16 vs. 0.56 + /- 0.13 m/s ; P < 0.01 ) , and preejection/ejection time ( PEP/ET ) ratio ( 0.72 + /- 0.05 vs. 0.57 + /- 0.06 ; P < 0.03 ) and a lower CVI ( P < 0.0001 ) than controls . CVI was inversely related to TSH level ( P < 0.0001 ) and PEP/ET ratio ( P < 0.01 ) . L-T(4)-treated patients showed a significant reduction of the PEP/ET ratio ( P < 0.05 ) , peak A ( P < 0.05 ) , and isovolumic relaxation time ( P < 0.05 ) along with a normalization of CVI . Conversely , no changes were observed in the placebo-treated group . In conclusion , sHT affects both myocardial structure and contractility . These alterations may be reversed by L-T(4 ) therapy Sub clinical hypothyroidism ( sHT ) is associated with dyslipidemia and enhanced cardiovascular risk . We assessed carotid artery intima-media thickness ( IMT , high-resolution ultrasonography ) and lipoprotein profile in 45 sHT patients ( aged 37 + /- 11 yr ) at baseline and after 6 months of r and omized , placebo-controlled L-T(4 ) replacement .  In comparison with 32 age- and sex-matched controls , sHT patients had elevated total and low-density lipoprotein ( LDL ) cholesterol and ApoB levels ( P = 0.002 , P = 0.0007 , and P = 0.01 , respectively ) and higher mean-IMT values ( P < 0.0001 ) . In stepwise regression analysis , mean-IMT was positively related ( r(2 ) = 0.71 , P < 0.0001 ) to age , TSH , and LDL cholesterol . L-T(4 ) replacement significantly reduced both total and LDL cholesterol ( P < 0.0001 for both ) and mean-IMT ( by 11 % , P < 0.0001 ) . The decrement in IMT was directly related to the decrements of both total cholesterol and TSH ( P = 0.02 and P = 0.0001 , respectively ) . We conclude that early carotid artery wall alterations are present in sHT patients . Whether such IMT increase is related to an early atherosclerotic involvement of the arterial wall can not be clearly decided on the basis of the present results . However , the fact that L-T(4 ) replacement therapy was able to improve both the atherogenic lipoprotein profile and intima-media thickening suggests that lipid infiltration of arterial wall may represent a major mechanism underlying IMT increase in sub clinical hypothyroidism OBJECTIVE To evaluate the effects of physiologic doses of levothyroxine replacement on the lipoprotein profile in patients with sub clinical hypothyroidism ( SCH ) . METHODS In a prospect i ve , double-blind , placebo-controlled study , we enrolled 120 patients --mostly , but not exclusively , premenopausal women -- with SCH . Patients were r and omly assigned to either a levothyroxine-treated group ( n = 60 ) or a placebo ( control ) group ( n = 60 ) .  Total cholesterol ( TC ) , low-density lipoprotein cholesterol ( LDL-C ) , high-density lipoprotein cholesterol ( HDL-C ) , and triglycerides ( TG )  were measured before and 52 weeks after assignment to either group . RESULTS In the levothyroxine-treated group , the lipoprotein mean values before and after the 52-week study were as follows : TC , 5.05 + /- 0.98 mmol/L versus 4.74 + /- 0.87 mmol/L ( P<.0001 ) ; LDL-C , 3.30 + /- 0.90 mmol/L versus 2.89 + /- 0.59 mmol/L ( P<.01 ) ; TG , 1.18 + /- 0.71 mmol/L versus 0.95 + /- 0.53 mmol/L ( P<.002 ) ; and HDL-C , 1.20 + /- 0.33 mmol/L versus 1.19 + /- 0.32 mmol/L ( P = .29 ) . In the control group , TC , HDL-C , and TG values remained unchanged after 52 weeks in comparison with baseline , but LDL-C mean values increased from 2.79 + /- 0.60 mmol/L to 3.11 + /- 0.77 mmol/L , a change that was statistically significant ( P<.001 ) . At the end of the study , the lipid profile changes between levothyroxine-treated and control groups were compared . Total cholesterol and LDL-C were significantly lower in the levothyroxine-receiving group ( P<.029 and P<.0001 , respectively ) in comparison with the control group . The difference did not reach statistical significance for TG and HDL-C values . CONCLUSION In premenopausal women , SCH has a negative effect on the lipoprotein profile and may translate into a sizable cardiovascular risk if left untreated BACKGROUND : Previous studies have suggested an association between sub clinical hypothyroidism and coronary artery disease that could be related to changes in serum lipids or endothelial dysfunction . METHODS : Thirty-two female sub clinical hypothyroidism patients were r and omly assigned to 12 months of L-thyroxine replacement or no treatment . Endothelial function was measured by the flow-mediated vasodilatation of the brachial artery , as well as mean carotid artery intima-media thickness , and lipid profiles were studied at baseline and after 12 months of follow-up . RESULTS : The mean ( ±SD ) serum thyroid-stimulating hormone levels in the L-thyroxine replacement and control groups were 6.09±1.32 and 6.27±1.39 µUI/ml , respectively . No relationship between carotid artery intima-media thickness or brachial flow-mediated vasodilatation and free T4 and serum thyroid-stimulating hormone was found . The median L-T4 dose was 44.23±18.13 µg/day . After 12 months , there was a significant decrease in the flow-mediated vasodilatation in the sub clinical hypothyroidism control group ( before : 17.33±7.88 to after : 13.1±4.75 % , p = 0.03 ) , but there were no significant differences in flow-mediated vasodilatation in the L-thyroxine treated group ( before : 16.81±7.0 to after : 18.52±7.44 % , p = 0.39 ) . We did not find any significant change in mean carotid intima-media thickness after 12 months of L-thyroxine treatment . CONCLUSION : Replacement therapy prevents a decline in flow-mediated vasodilatation with continuation of the sub clinical hypothyroidism state . Large prospect i ve multicenter placebo-controlled trials are necessary to investigate endothelial physiology further in sub clinical hypothyroidism patients and to define the role of L-thyroxine therapy in improving endothelial function in these patients BACKGROUND Mild sub clinical hypothyroidism ( SCH ) affects a large number of people and is known to be a risk factor for dyslipidemia . However , whether mild SCH patients should be treated with L-thyroxine to improve lipid profiles remains controversial . In addition , it is also unclear whether all mild SCH patients can benefit from L-thyroxine treatment , regardless of basal thyrotropin or lipid levels . This study aim ed to assess the effects of L-thyroxine replacement therapy on the lipid profiles of mild SCH patients . METHODS This open-label r and omized controlled trial was performed in Ningyang County , Sh and ong Province , China . A total of 378 mild SCH patients with diagnoses confirmed by two thyroid function tests were r and omly assigned to either the intervention group ( L-thyroxine replacement therapy ) or the control group ( no treatment ) . The primary outcome was a change in serum total cholesterol ( TC ) concentration . RESULTS In all , 369 participants completed the 15-month follow-up period .  Reduced TC concentrations were more prominent in the intervention group than they were in the control group ( -0.41 mmol/L vs. -0.17 mmol/L ; p = 0.012 ) , and changes in low-density lipoprotein cholesterol levels exhibited the same trend . Subgroup analyses were performed to assess the effects of L-thyroxine in patients with different thyrotropin or TC levels . When the study population was stratified according to basal thyrotropin concentration , all patients who had received L-thyroxine showed reduced TC levels ( p < 0.001 ) . The treatment was similarly beneficial for all patients , regardless of basal TC level . Even for subjects with TC levels < 5.18 mmol/L , serum TC concentrations remained unchanged in the intervention group ( p = 0.936 ) but increased by 0.35 mmol/L in the control group ( p = 0.004 ) . CONCLUSIONS The findings suggest that mild SCH patients could benefit from L-thyroxine treatment to improve lipid profiles , regardless of basal thyrotropin or TC concentrations Although muscle metabolism and exercise capacity seem to be affected in patients with sub clinical hypothyroidism , there is little evidence indicating improvement of the exercise tolerance due to levothyroxine ( L-T(4 ) ) replacement . The aim of the present study was to verify possible cardiopulmonary changes during exercise in patients with sub clinical hypothyroid 
    Output:
    
Results from the included r and omized controlled trials suggested no benefit of treatment for sub clinical hypothyroidism for the large majority of outcomes .
This review found moderate to very low- quality evidence on the benefits and harms of treatment for sub clinical hypothyroidism , with most of the evidence showing no benefit of treatment