Increased TSH in obesity: Evidence for a BMI-independent association with leptin

AIM

This study aimed to determine whether the association between thyroid-stimulating hormone (TSH) and body mass index (BMI) is related to leptin concentration in obese individuals.

METHODS

Plasma TSH and leptin assays were performed in 800 consecutive patients, hospitalized for a nutritional checkup, with a BMI ≥ 30 kg/m(2). Various anthropometric, hormonal and metabolic parameters, including age, weight, BMI, insulin, leptin and TSH, were measured or calculated. Univariate and multivariate regression analyses were performed to identify any significant relationships between these parameters. Also, characteristics of the patients in the lowest and highest quartiles of TSH distribution were compared.

RESULTS

TSH was positively correlated with both BMI and leptin. When multiple regression analysis was performed, TSH and leptin maintained a significant association independent of BMI. Patients in the fourth quartile of TSH distribution displayed higher BMI and higher leptin levels in comparison to the first quartile.

CONCLUSION

Our study has confirmed an increase in TSH in conjunction with BMI in obese subjects. This increase was correlated with leptin independently of BMI. It is hypothesized that the increase in TSH observed in obese subjects was the consequence of both fat mass accumulation and a positive energy-balance.

Good practice guide for cervical ultrasound scan and echo-guided techniques in treating differentiated thyroid cancer of vesicular origin

Good practice guide for cervical ultrasound scan and echo-guided techniques in treating differentiated thyroid cancer of vesicular origin. American, European and French Recommendations for the treatment of differentiated vesicular thyroid cancer were recently published. Cervical ultrasound scanning is now considered a key examination in the follow-up of these cancers. This examination is noninvasive, easy to perform and to obtain, is not costly, but remains operator-dependent. To date, there are no recommendations published that assemble all the technical aspects, results, indications and the limits of this examination in the initial medical report and the follow-up of these cancers. In order to standardise the procedure and validate the quality of the examination, a workgroup made up of a panel of experts particularly involved in carrying out ultrasound scans was set up. The aim was to draw up a good practice guide for performing cervical ultrasound scans and echo-guided techniques in treating patients with differentiated thyroid cancer of vesicular origin. The main objectives are to: (a) standardise the procedure and reports, (b) define the criteria for establishing whether lesions identified during a cervical ultrasound scan are malignant or benign, (c) standardise the indications for carrying out cytological tests and an in situ assay of markers, (d) help doctors to select the patients who ought to receive a cervical ultrasound scan and or cytological tests, (e) discuss how frequently the examinations should be carried out depending on the risk of recurrence.

Comparison of metabolic deterioration between insulin analog and regular insulin after a 5-hour interruption of a continuous subcutaneous insulin infusion in type 1 diabetic patients

An interruption of continuous sc insulin infusion (CSII) of the insulin analog lispro should result in a more rapid metabolic deterioration of type 1 diabetic patients because of its pharmacokinetic characteristics. We analyzed the metabolic changes occurring during a 5-h interruption of CSII and the 5 h after restarting the pump in 10 type 1 diabetic patients. The study was a randomized, cross-over, open label design comparing insulin analog [Lispro (LP)] and regular insulin [Velosuline (VE)]. Plasma glucose, free insulin, glucagon, betahydroxybutyrate (beta-OHB), and nonesterified fatty acids (NEFA) were measured every hour from 0700 h (time zero) to 1700 h (600 min). After stopping CSII, the plasma glucose level was significantly higher in the LP group than in the VE group (P < 0.05-0.01). The plasma free insulin level decreased significantly with the two treatments, but was significantly lower with LP than with VE (P < 0.05-0.01). Plasma NEFA increased more rapidly and was significantly higher in the LP group than in the VE group (P < 0.01-0.05). Plasma beta-OHB increased earlier with LP, but was not statistically different between the treatments. After restarting the pump, plasma glucose decreased with LP, but continued to increase with VE, and the plasma free insulin peak occurred earlier and was greater with LP than with VE (P < 0.05). Plasma NEFA and beta-OHB levels decreased significantly with the two treatments, but more dramatically with LP treatment. Thus, a short interruption of Lispro in CSII is associated with an earlier, greater metabolic deterioration, but Lispro corrected this metabolic deterioration more effectively.

[Analytical evaluation of third generation TSH assay. Application to the exploration of thyrotropin suppression in differentiated thyroid cancer]

Intravenous TRH (200 micrograms Protiréline) injection was performed in 137 patients who had undergone thyroidectomy for differentiated thyroid carcinoma and treated by a suppressive thyroid therapy. Serum thyroid stimulating hormone (TSH) was measured before and 30 minutes after the injection. 143 tests were performed. The TSH method used was a chemiluminometric assay (Chiron Diagnostics). We study the analytical characteristics of the method. The limit of detection was 0.003 mUI/l. Interassay precision showed a functional sensitivity of 0.015 m UI/l with 20% interassay CV in agreement with the third generation criterion. There was a good correlation between TSH values at T0 and T30 minutes. In 143 tests, 40 (28%) showed a basal TSH value less than 0.003 mUI/l; delta TSH (TSH at T30-TSH at T0) was less than 0.015 mUI/l in about 68% of the cases and less than 0.031 mUI/l for the others. In 20% of the tests (29) TSH T0 were between 0.003 and 0.015 mUI/l and delta TSH less than 0.204 mUI/l. Finally the 74 remaining tests with a basal TSH value higher than the functional sensitivity of the method showed delta TSH less than 0.4 mUI/l if the TSH T0 was less than 0.05 mUI/l. The delta TSH remained less than 0.6 mUI/l if the TSH T0 was less than 0.1 mUI/l. Inversely, if TSH T0 was higher than 0.1 mUI/l delta TSH could be higher than 1.0 mUI/l. Third generation TSH assay allows us to abandon TRH test for the follow-up of thyroidectomized patients with suppressive thyroid hormonotherapy in so far as TSH assay is well established. We conclude that a basal TSH less than the functional sensitivity (0.015 mUI/l) can predict a TSH response to TRH stimulation test less than 0.2 mUI/l.

Effects of drug administration on gonadotropins, sex steroid hormones and binding proteins in humans

The possible mechanisms by which the administration of drugs may alter the gonadal function in humans are considered in this review. Based on personal data, and on data published in the literature, the following events may occur: (1) blockade of gonadal steroidogenesis; (2) interaction of drug(s) with the steroid-binding protein system in plasma, and (3) interference of drug(s) at the level of the feedback control of gonadotropin secretion. Representative examples of the above mechanisms are as following: (1) Ketoconazole possesses inhibitory effects in vitro on cytochrome P-450. When given in adult males, it decreased the plasma concentrations of testosterone (T) and androstenedione and increased 17 alpha-hydroxyprogesterone levels, suggesting that this drug acts in vivo on gonadal steroidogenesis by blocking the 17,20-lyase. (2) Danazol is a progestagen with high affinity for sex steroid-binding protein (SBP); when given in high dosages in normal males, it increased rapidly the dialyzable fraction (percent protein unbound or free fraction) of T. This suggests that by interacting with the binding sites of SBP, danazol and/or its metabolites displace the fraction of T bound to SBP. However, in males as well as in females, the long-term administration of danazol decreased also the binding capacity of SBP, and consequently increased the free fraction of sex steroid hormones. (3) Dihydrotestosterone (DHT), the most active androgen in many target cells, given at therapeutic dosages to adult males, resulted in a decrease in plasma concentrations of luteinizing hormone (LH) and T, without any significant change in the percent of free T, even though the affinity of DHT for SBP is higher than that of T. This suggests that the main effect of DHT is to inhibit gonadotropin secretion at the central level. (4) Flutamide, a nonsteroidal antiandrogen, increased both LH and T levels, demonstrating its pure antiandrogenic activity on gonadotropin secretion. The consequence(s) of the effects of such drugs on the production, the metabolic clearance rate and the bioavailability of sex steroid hormones are discussed.