hypothyroidism is a complex disorder characterized by an increase in body weight . about 1530% of hypothyroid patients
are reported to be overweight and sufficient replacement therapy generally induces significant weight loss . however ,
7% of the patients were observed to preserve their original weight in spite of the successful treatment . in hypothyroid patients , body fat content
this effect is attributed to the reduction of lipid metabolism in hypothyroidism [ 3 , 4 ] .
nevertheless , the expected decrease in body fat content is not observed with replacement therapy in a few studies [ 5 , 6 ] . in a recent study , it was reported that l - thyroxine therapy resulted in an increase in body mass index ( bmi ) independently from thyroid - stimulating hormone ( tsh ) levels . in another study , the decrease in body weight of hypothyroid patients treated with l - thyroxine was found to be related with the excretion of excess body water associated with the improvement of myxedema state instead of the change in body adiposity .
all these data caused requery of the effects of l - thyroxine replacement therapy on body adiposity in hypothyroid patients .
although there are many methods to determine body fat content , bmi and waist circumference are widely used due to their easiness and low cost [ 1012 ] .
measurement of skin fold thickness ( sft ) is another simple method used for this purpose [ 13 , 14 ] .
bioelectrical impedance analysis system ( bia ) is an easy and a cheap method which helps to identify different body compartments : body lipid percentage , fat - free body mass , and total body fluid . in this study
, we aimed to observe the effects of midterm thyroid replacement therapy on body fat content determined with various anthropometric methods and a bioelectrical impedance method .
this study was performed in a university hospital 's endocrinology and metabolism diseases outpatient clinic and it was designed as a prospective and controlled study . as body fat content
is known to be different within the two genders , only females were asked to participate .
subjects with hypothyroidism due to autoimmune thyroiditis who did not administer l - thyroxine replacement therapy before , with tsh levels greater than 10 
miu / l and aged between 18 and 50 years , were enrolled to the study . for the chronic autoimmune thyroiditis diagnosis ,
the criteria used were elevation of at least one of the antithyroglobulin or antithyroid peroxidase autoantibodies and/or shown ultrasonographic changes due to thyroiditis .
exclusion criteria for the study were ( 1 ) postmenopausal women , ( 2 ) smoking , ( 3 ) patients using drugs which may affect thyroid functions like lithium , amiodarone , steroids , beta blockers , or interferon , ( 4 ) patients using drugs which may affect body water - lipid homeostasis like diuretics or oral contraceptives , ( 5 ) patients with chronic renal failure , hepatic failure , congestive heart diseases , malnutrition , or malignant diseases , ( 6 ) pregnant women , and ( 7 ) patients with other known endocrine disorders . a control group with similarly aged healthy women volunteers
this study was approved by bakent university institutional review board and ethics committee ( project no .
patients who did not come to control visits , did not reach target tsh levels ( 0.454.12 
miu / l ) , became pregnant , or used drugs which might affect the results during follow - ups were excluded from the study .  
after 12 hours of fasting , weight and height of the patients and controls were measured with a standard steelyard at the first visit .
waist circumference was measured at the midpoint between the iliac crest and lower rib margin .
subscapular , suprailiac , femur , biceps , and triceps skin fold thicknesses ( sft ) were measured by a caliper .
body fat percentage ( bfp ) was calculated with the data obtained via using the methods suggested by deurenberg , lean , and durnins for female gender [ 1719 ] :  bfp : 1.2  bmi + 0.23  age ( year )  5.4 ( by deurenberg for bmi ) ,  bfp : 0.439  waist circumference ( cm ) + 0.221  age ( year )  9.4 ( by lean for waist circumference ) ,  bfp : 1.33 ( triceps sft +  subrascapular sft )  0.013 ( triceps sft + subscapular sft )  2.5
( by deurenberg for bmi ) , bfp : 0.439  waist circumference ( cm ) + 0.221  age ( year )  9.4 ( by lean for waist circumference ) , bfp : 1.33 ( triceps sft +  subrascapular sft )  0.013 ( triceps sft + subscapular sft )  2.5
body fat measurements were performed by using a foot - to - foot pressure electrode bioelectrical impedance analysis contact system ( bia ) ( tanita tbf-105 , tanita corp . , tokyo , japan ) . before testing , subjects were required to adhere to the bia testing guidelines : ( 1 ) not to eat or drink ( especially caffeinated products ) within 4 hours of the test , ( 2 ) not to consume alcohol within 48  h of the test , ( 3 ) to avoid intense exercise within 12 hours of the test , ( 4 ) not to take diuretics within 7 days of the test , and ( 5 ) to empty bladder within 30 minutes of the test .
the procedure was performed while the subject was standing erect barefoot on the device 's footpads and wearing light clothes .
thyroid - stimulating hormone and free thyroxine ( ft4 ) levels were obtained from the venous blood sample of the forearm brachial veins and were studied with electrochemiluminescence immunoassay by using abbott - artitect analyzer ( chicago , il , usa ) .
anti - thyroid peroxidase levels were studied with electrochemiluminesans immunoassay by using modular e170 analyzer ( roche diagnostic , mannheim , germany ) .
then , each patient was given 1.6  mcg / kg / day l - thyroxine in order to reach the target tsh level ; the dosage was increased when indicated .
the subjects were advised not to change their dietary and exercise habits and all were called for regular control every six weeks . at the 6th and 18th months of follow - up ,
body fat percentages were recalculated and tsh measurements were reperformed by the same researcher using the methods mentioned above .
body fat percentages of the patients and the control group calculated by the mentioned formulas and bia during the initial 6- and 18- month visits were compared .
comparisons between continuous variables were applied with student 's t - test or one - way anova for normally distributed data and mann - whitney u test or kruscal wallis test for the data not - normally distributed .
prepost measures data were analyzed by paired t - test , wilcoxon tests or repeated measure analyses .
correlation coefficients were interpreted as either excellent relationship r  0.91 ; good 0.90  r  0.71 ; fair 0.70  r  0.51 ; weak 0.50  r  0.31 ; little or none r  0.3 ( ref ) .
forty - two patients as study group and 40 subjects as a control group were enrolled to the study .
thirty - one patients as a study group and 34 subjects as control group completed the study because of the exclusion criteria mentioned in section 2 .
the characteristics of the patients and control subjects at inclusion , at the 6th month , and at the 18th month of the study are shown in tables 1 and 2 .
mean tsh level at inclusion was 57.49  36.46  miu / l ( minimum : 10.12 , maximum : 100 ) , at the 6th month 1.26  1.35  miu / l , and at the 18th month , 1.38  1.09 
final mean l - thyroxine dose was 1.54  0.76  cg / kg / day
there was no significant difference between the patient group and the control group when mean ages were compared ( p = 0.63 ) .
mean tsh level at inclusion was 1.94  1,12  miu / l ( minimum : 0.52 and maximum : 4.1 ) , at the 6th month 1.76  1.01  miu / l , and at the 18th month 1.49  0.8  miu / l .
there was evident difference between initial mean tsh levels of the study group and control group ( p = 0.001 ) , while there was no statistically significant difference at the 6th and the 18th months ( p = 0.28 and 0.31 , resp . ) .
the comparisons of hypothyroid- and control - group characteristics during follow - up were given in table 3 .
the female gender is classified into the following groups regarding body fat measurements performed with tanita : the ones with bfp(% ) below 15 are regarded as thin , those between 15 and 22 as normal , those between 23 and 26 as overweight , those between 27 and 32 as obese , and the ones over 32 as morbid obese . considering this information ,
our hypothyroid - cases are grouped as obese throughout the follow - up , with bfp values 32.09  2.81 at initiation , 31.11  2.56 at the 6th month , and 31.02  2.77 at the 18th month .   in hypothyroid group ,
the mean body weight showed a slight decrease which did not exhibit statistical significance ( p = 0.36 at the 6th month and p = 0.34 at the 18th month ) . using the above - mentioned four methods ,
the bfp of each case at inclusion was compared with the value at the 6th and the 18th months . in the hypothyroid group ,
a slight decrease was observed but it was not significant ( table 1 ) .   during follow - up , sft measured from all sites were observed to decline but only those obtained from femur and biceps showed a statistically significant decrease ( p = 0.03 and p = 0.01 , resp . )
the decrease in thermogenesis and fat tissue metabolism and fluid retention are considered to be responsible for this situation . in this study , in spite of the fact that the participants achieved euthyroidism with adequate l - thyroxine replacement , we did not observe a significant decrease in body weight and body fat percentages .
our findings are compatible with the animal studies and human studies reporting statistically insignificant change in bfp following the treatment of hypothyroidism [ 2022 ] .  
the expected decrease in weight and body fat percentage was not observed in our study .
this issue may resulted from a few reasons ; one of them may be the increase in orexigenic response which can be triggered by increased thermogenesis . the persistence of hypothyroid milieu in the tissues in spite of normalized tsh levels may well be another explanation .  
although there was no difference by means of body weight , waist circumference , and bfp , there was a significant decrease in sft measured with a caliper .
this finding might be attributed to the decrease in subcutaneous mucopolysaccharides accumulation resulting from hypothyroidism .
this study has a few limitations . our inability to determine the fat percentages with the gold standard methods , computerized tomography or magnetic resonance imaging , was one of them .
but every patient being the control of his own and that all measurements being performed by the same researcher , we hope it may be appreciated .
however , our study results support current medical literature , and bigger studies with larger study groups are required to clarify these findings . due to the classification regarding body fat measurements performed with tanita ,
our subjects are grouped as obese , although they are considered to be overweight for bmi .
this finding may be attributed to the increase in body fat resulting from hypothyroidism .   in conclusion , in spite of the correction of hypothyroidism , at the 6th and 18th months of follow - up , our cases did not exhibit significant changes in terms of body weight , waist circumference , and bfp determined via the methods mentioned above .
this condition might be explained by the reduction of subcutaneous mucopolysaccharides which were deposited during the hypothyroid state .
 
 aim . 
 we aimed to observe the effects of l - thyroxine replacement therapy on body fat content determined with various anthropometric methods and a bioelectrical impedance analysis method in patients with hypothyroidism . methods . 
 forty - two women with naive autoimmune hypothyroidism were included . 
 also , 40 healthy participants were enrolled as a control group . 
 weight , body mass index , waist circumference , and subscapulary , suprailiac , femur , biceps , and triceps skin fold thicknesses were measured . 
 body fat percentages were calculated and body fat measurements were performed . 
 euthyroidism was maintained with l - thyroxine . at the 6th and 18th month , of therapy , measurements were reperformed . 
 results . 
 mean tsh levels were 57.49  36.46  
 miu / l in hypothyroid group and 1.94  1.12  miu / l in control subjects at admission . in hypothyroid patients , 
 calculated body fat percentages were greater than those of the control subjects during follow - up . 
 body fat percentage of each hypothyroid case decreased at 6- and 18-month controls , but the decrements were statistically insignificant . 
 although skin fold thicknesses measured from all sites were observed to decline , only those obtained from femur and biceps showed a significant decrease ( p = 0.03 and p = 0.01 , resp . ) . 
 discussion . 
 correction of hypothyroidism did not cause any improvement in body weight and body fat percentage . 
 the decrease in skin fold thicknesses might probably result from the reduction in subcutaneous mucopolysaccharide deposits . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion