Detection of macro-thyrotropinaemia in patients with Hashimotos thyroiditis and subclinical hypothyroidism

The level of thyroid stimulating hormone is one of the diagnostic indicators of thyroid function. In subclinical hypothyroidism, its concentration in the blood serum increases, while the level of thyroid hormones remains normal. One of the reasons for this is the phenomenon of macrotyrotropinemia, in which the macro isoforms of thyrotropin (a complex of thyrotropic hormone with immunoglobulin) are present in the blood. It is assumed that the biological activity of macrotyrotropin is low, and may accumulate in the circulation, causing a falsely elevated level of thyroid-stimulating hormone in serum. The aim of this study is to identify the nature and prevalence of the macrothyrotropinemia phenomenon among patients with subclinical hypothyroidism in presence of autoimmune thyroiditis and a group of healthy donors. Materials and methods: Fifty serum samples of venous blood served as the material for the study: 30 patients with subclinical hypothyroidism in presence of autoimmune thyroiditis; 10, with manifesting hypothyroidism, 10 conditionally healthy donors without thyroid gland pathology (control group). The group was derived from results of the clinical laboratory at the Clinical Hospital at the Kazan station railway. Patients’ blood serum was screened for the presence of macrotrorotropin by polyethylene glycol precipitation method, followed by analysis by gel filtration chromatography. Results of this study were as follows: screening of blood sera was performed by gel filtration and affinity chromatography. Polyethylene glycol was shown to precipitate 50 to 100% serum thyrotropin, of which true macrotrothropin makes 56-98%. In the patients with subclinical hypothyroidism with a thyroid-stimulating hormone level of more than 10 pIU/ml, a trend towards an increase in the level of macrothyrotrophinaemia has been shown. The content of macrotyrotropin complex in patients with subclinical hypothyroidism, in whom the level of antibodies to thyroperoxidase is > 500 U/L, is significantly higher if compared to the patients with manifesting hypothyroidism. Elevated levels of antibodies to thyroperoxidase can lead to the generation of macrotyropin. Our findings have shown that the phenomenon of macrothyrotropinemia is quite common in patients with subclinical and manifesting hypothyroidism with Hashimoto thyroiditis (53.3%) and in control group (25%). Macrotyrotropin complex probably consists of thyrotropin and IgG. Patients with a thyroid-stimulating hormone level of > 10 pIU/ml are candidates for screening for the presence of the macrotyrotropin complex.The activity of the autoimmune process may correlate with the phenomenon of macrothyrotropinemia. The results can be used to develop an additional tool when choosing therapy in clinical practice

Paleomagnetic study of Cenozoic sediments from the Zaisan basin (SE Kazakhstan) and the Chuya depression (Siberian Altai): tectonic implications for central Asia

International audienceThis paper presents new paleomagnetic results on Cenozoic rocks from northern central Asia. Eighteen sites were sampled in Pliocene to Miocene clays and sandy clays of the Zaisan basin (southeastern Kazakhstan) and 12 sites in the upper Oligocene to Pleistocene clays and sandstones of the Chuya depression (Siberian Altai). Thermal demagnetization of isothermal remanent magnetization (IRM) showed that hematite and magnetite are the main ferromagnetic minerals in the deposits of the Zaisan basin. Stepwise thermal demagnetization up to 640-660 °C isolated a characteristic (ChRM) component of either normal or reverse polarity at nine sites. At two other sites, the great circles convergence method yielded a definite direction. Measurements of the anisotropy of magnetic susceptibility showed that the hematite-bearing sediments preserved their depositional fabric. These results suggest a primary origin of the ChRM and were substantiated by positive fold and reversal tests. The mean paleomagnetic direction for the Zaisan basin ( D=9°, I=59°, k=19, α95=11°) is close to the expected direction derived from the APW path of Eurasia [J. Geophys. Res. 96 (1991) 4029] and shows that the basin did not rotated relative to stable Asia during the Tertiary. In the upper Pliocene-Pleistocene sandstones of the Chuya depression, a very stable ChRM carried by hematite was found. Its mean direction ( D=9°, I=46°, k=25, α95=7°) is characterized by declination close to the one excepted for early Quaternary, whereas inclination is lower. In the middle Miocene to lower Pliocene clays and sandstones, a stable ChRM of both normal and reverse polarities carried by magnetite was isolated. Its mean direction ( D=332°, I=63°, k=31, α95=4°) is deviated with respect to the reference direction and implies a Neogene, 39±8° counterclockwise rotation of the Chuya depression relative to stable Asia. These results and those from the literature suggest that the different amount of rotation found in the two basins is related to a sharp variation in their tectonic style, predominantly compressive in the Zaisan basin and transpressive in the Siberian Altai. At a larger scale, the pattern of vertical axis rotations deduced from paleomagnetic data in northern central Asia is consistent with the hypothesis of a large left-lateral shear zone running from the Pamirs to the Baikal. Heterogeneous rotations, however, indicate changes in style of faulting along the shear zone and local effect for the domains with the largest rotations