Background: The absorption of levothyroxine (LT4) is affected by many factors. Bariatric surgery is recommended in severely obese patients. The aim of this study was to determine the consequences of bariatric surgery on LT4 pharmacokinetic parameters, and to identify the regions of the gastrointestinal tract where LT4 is absorbed in patients with severe obesity before and after surgery. Methods: We studied 32 severely obese nonhypothyroid patients who underwent sleeve gastrectomy (SG; n=10), Roux-en-Y gastric bypass (RYGBP; n=7), or biliopancreatic diversion with long limbs (BPD-LL; n=15). Before surgery, from 8:00 a.m., blood samples were collected before and every 30 minutes after the oral administration of a solution of 600 μg of LT4. The same procedure was repeated 35 days after surgery. We estimated the pharmacokinetic parameters of LT4 before and after surgery, including the area under the curve (AUC), the peak thyroxine concentration (C_max), and the time to peak thyroxine concentration (T_max). Results: Following surgery, in the SG group, the mean AUC was higher than it was before surgery (18.97±6.01 vs. 25.048±6.47 [μg/dL]·h; p<0.01), whereas the values of C_max and T_max were similar to those before surgery. In the RYGBP group, mean AUC, C_max, and T_max were similar before and after surgery. In the BPD-LL group, mean AUC and C_max were higher after surgery than before (14.18±5.64 vs. 25.51±9.1 [μg/dL]·h, p<0.001; 5.62±1.34 vs. 8.16±2.57 μg/dL, p<0.001, respectively), whereas T_max was similar. Conclusions: The pharmacokinetic parameters of LT4 absorption are improved following SG and BPD-LL types of bariatric procedures. We conclude that the stomach, the duodenum, and the upper part of the jejunum are not sites for LT4 absorption, because in the above-mentioned bariatric procedures these are bypassed or removed.

Background: Suppressive or replacement doses of levothyroxine (LT4) are affected by the rate and extent of the active ingredient absorbed, as well as by the lean body mass. Obesity has reached epidemic proportions worldwide and is related with many comorbidities. The aim of this study was to determine the pharmacokinetic parameters of LT4 in severely obese individuals and compared them with similar data in lean control subjects. Methods: We studied 62 euthyroid subjects who had negative tests for anti-thyroid peroxidise antibodies (Ab-TPO). Thirty eight of these subjects were severely obese but otherwise healthy (severe obese subjects [SOS] group). Twenty-four were healthy control subjects (control group), with a body mass index of 23.3 ± 1.7 kg/m². Subjects received 600 μg oral sodium LT4 after an overnight fast. Serum triiodothyronine (T3), T4, and thyroid-stimulating hormone were measured at baseline. Serum T4 and T3 was measured 0.5, 1, 1.5, 2, 2.5, 3, and 4 hours after LT4 administration. Results: Baseline serum T4 and thyroid-stimulating hormone concentrations were higher in the SOS group than in the control group; serum T3 was similar in the two groups. The corrected area under the curve and the maximum T4 concentration after LT4 administration were lower, whereas the time to maximum concentration from the baseline was higher in SOS than in the control group. The estimated plasma volume was higher in the SOS than in the control group. Mean serum T3 levels increased gradually during the four hours after LT4 administration in the control group. In contrast, they decreased gradually in the SOS group. Conclusions: Severely obese individuals may need higher LT4 suppressive or replacement doses than normal-weight individuals due, among other factors, to impaired LT4 pharmacokinetic parameters. The latter could be attributed to their higher plasma volume and/or to delayed gastrointestinal LT4 absorption. T4 conversion to T3 might be defective in severe obesity.

Exercise challenges homeostasis and establishes a new dynamic equilibrium. Elite Rhythmic Gymnasts (RG’s) begin exercise at an early age, undergo physical and psychological stress, and adopt negative energy balance to retain a lean physique. The aim of the present study was to evaluate the effect of negative energy balance, acute and chronic exercise on salivary adiponectin, resistin and visfatin levels and their interaction with salivary cortisol, and insulin levels in elite RG’s. This study is unique in character, as all variables were assessed on the field of competition. The study included 51 elite RG’s participating in “Kalamata 2010 World Cup” in Kalamata, Greece on April 2010. Twenty-seven healthy age-matched girls were used as controls. Anthropometric values were assessed; baseline and post exercise salivary cortisol, insulin, adiponectin, resistin, and visfatin levels were measured. Comparisons regarding hormonal features between RG’s and controls were adjusted for BMI and body fat percentage. Salivary adiponectin levels were higher (p<0.05) and visfatin lower (p=0.094) in RG’s compared with controls, while no significant changes were observed regarding salivary cortisol, insulin, and resistin levels. In elite RG’s acute intensive anaerobic exercise led to increased salivary insulin levels (p<0.001), reduced salivary adiponectin (p<0.001) and visfatin levels (p<0.05), and no changes in salivary resistin levels. Moreover, diurnal variation of salivary cortisol was lost. In elite RG’s salivary adiponectin is upregulated and salivary visfatin is downregulated after chronic intensive exercise and negative energy balance, while both salivary adiponectin and visfatin levels are suppressed after short term intensive anaerobic exercise.

Adequate dietary iodine intake is necessary for normal thyroid gland function at all times, and most particularly during pregnancy. Increased iodine loss is cited, among other factors, as responsible for the increased iodine demand in this period. Our aim was to compare renal iodine excretion between women during all three pregnancy trimesters with that of their spouses and thereby to estimate the iodine intake in an a large sample of pregnant women in urban areas in Greece. Four hundred twenty-four healthy pregnant women were included prospectively (residents of Athens n=218, residents of Patras n=206). The spouses of 177 of these women following the same diet were also studied. Determinations included serum FT4, TSH and aTPO and urinary iodine excretion (UIE). No difference was found either in median UIE throughout pregnancy or between the UIE of the pregnant women and their spouses during the trimesters. Throughout pregnancy, mild iodine deficiency was noted and was classified as mild in 60%, moderate in 30% and severe in 10% of the women studied. Users of iodized salt had significantly higher median UIE compared with non-users. Serum FT4 levels decreased and TSH increased as pregnancy progressed. Our study indicates that renal iodine excretion is not increased during pregnancy. This finding needs to be confirmed by further investigation in other populations with different iodine intakes. Thus, increased iodine requirements in pregnancy are possibly due to extra-renal causes. The population of pregnant women in Greek urban areas is mildly-and often moderately and severely-iodopenic and needs to be treated accordingly.

Background: Amiodarone-induced thyrotoxicosis (AIT) is a common and deleterious side effect of amiodarone use. There are two types of AIT, characterized by distinct pathogenic mechanisms and, hence, different treatments. Discriminating between type 1 (AIT1) and type 2 (AIT2) AIT is often very challenging. Beta-glucuronidase (β-G) is a lysosomal enzyme released into the extracellular fluid during inflammation. Objectives: To examine whether the determination of the plasma activity of β-G is useful in distinguishing AIT1 from AIT2. Methods: The study included 67 subjects: 9 with AIT1, 9 with AIT2, 14 with hyperthyroidism due to Grave’s disease or toxic multinodular goiter, 14 with subacute thyroiditis, and 21 euthyroid controls. Thyroid function tests and plasma β-G activity were determined in all participants, while thyrotoxic patients also underwent thyroid ultrasound/scintigraphy and urine iodine excretion assessment. Results: Plasma β-G activity (expressed as mean ± SD in nmol 4-methylumbelliferone [4-MU]/mL plasma/h) in AIT2 was higher compared to AIT1 (2,263.6 ± 771 vs. 1,101.8 ± 201.9, p < 0.05) and similar to subacute thyroiditis (2,263.6 ± 771 vs. 2,083.2 ± 987.5, p = ns). β-G activity did not differ significantly between AIT1 and controls (1,101.8 ± 201.9 vs. 954.6 ± 248.6, p = ns). ROC curve analysis revealed that β-G activity had a high predictive value for destructive processes, namely AIT2 and subacute thyroiditis (AUC 0.846, 95% CI 0.748–0.943) and a cut-off value of 1,480.5 nmol 4-MU/mL plasma/h was able to discriminate between destructive and non-destructive thyroid conditions with 74% sensitivity and 82% specificity. Conclusion: In our study, plasma β-G activity performed well in distinguishing AIT1 from AIT2. Further studies are warranted to establish its usefulness as a discriminator between the two AIT types.