Magnetic Properties of Bismuth Ferrite Nanopowder Obtained by Mechanochemical Synthesis

Multiferroic bismuth ferrite (BiFeO3) nanopowders have been obtained in room temperature by mechanical synthesis. Depending on the post-synthesis processing the nanopowders have exhibited differences in the mean sizes, presence of amorphous layer and/or secondary phases. Extended magnetic study performed for fresh, annealed and hot-pressed nanopowders have revealed substantial improvement of the magnetic properties in the as-prepared powder.Comment: 4 pages, 3 figure

Do IGF-I concentrations better reflect growth hormone (GH) action in children with short stature than the results of GH stimulating tests? Evidence from the simultaneous assessment of thyroid function

<p>Abstract</p> <p>Background</p> <p>The diagnosis of growth hormone (GH) deficiency (GHD) in short children seems unquestionable when both GH peak in stimulating tests (GHST) and IGF-I concentration are decreased. However, the discrepancies between the results of GHST and IGF-I secretion are observed. It seems purposeful to determine the significance of GHST and IGF-I assessment in diagnosing GHD. The relationship between GH secretion and thyroid function, as well as GH influence on the peripheral thyroxine (T₄) to triiodothyronine (T₃) deiodination, mediated by IGF-I, were identified. Thus, clear differences in thyroid function between GH-deficient and non-GH-deficient subjects should exist.</p> <p>Methods</p> <p>Analysis comprised 800 children (541 boys), age 11.6 ± 3.1 years (mean ± SD), with short stature, in whom two (2) standard GHST (with clonidine and with glucagon) were performed and IGF-I, free T₄(FT₄), free T₃(FT₃) and TSH serum concentrations were assessed. The patients were qualified to the following groups: GHD - decreased GH peak in GHST and IGF-I SDS (n = 81), ISS - normal GH peak and IGF-I SDS (n = 347), low GH - normal IGF-I SDS, and decreased GH peak (n = 212), low IGF - decreased IGF-I SDS, and normal GH peak (n = 160). The relationships among the results of particular tests were evaluated.</p> <p>Results</p> <p>In the groups with decreased IGF-I concentrations (GHD Group and low IGF Group), the more severe deficit of height was observed, together with higher TSH and FT₄but lower FT₃levels than in groups with normal IGF-I concentrations (ISS Group and low GH Group), independently of the results of GHST. TSH, FT₄and FT₃concentrations were - respectively - similar in two groups with decreased IGF-I secretion, as well as in two groups with normal IGF-I levels. Significant correlations were found between patients' height SDS and IGF-I SDS, between FT₃and IGF-I SDS (positive), and between FT₄and IGF-I SDS (negative), with no correlation between GH peak and any of the parameters analyzed.</p> <p>Conclusion</p> <p>The assessment of thyroid function in children with short stature provides the evidence that measurement of IGF-I concentration may be a procedure reliable at least to the some degree in diagnosing GHD as the results of GHST.</p

Limited usefulness of the test of spontaneous growth hormone (GH) nocturnal secretion as a screening procedure in diagnosing GH deficiency in children with short stature

[b]introduction and objective[/b]. In Poland, the assessment of nocturnal GH secretion has gained the status of screening test; however, this procedure is not included in international recommendations. The aim of the study was to assess the accuracy and predictive value of the test of nocturnal GH secretion as a screening procedure in diagnosing GHD, and to check the adequacy of the cut-off value for GH peak in this test on the level of 10 ng/ml. [b]materials and methods. [/b]The analysis comprised the data of 1,000 children with short stature. In all the patients, GH secretion was assessed in a screening test (after falling asleep) and in 2 stimulating tests (reference tests), with simultaneous assessment of IGF-I secretion before stimulating tests. The indices of screening test accuracy, likelihood ratios and predictive values were assessed. The cut-off level of GH peak after falling asleep, ensuring its 95% sensitivity, was calculated in ROC curve analysis. [b]results[/b]. Sensitivity of the screening test was 70.4%, while the specificity – 61.2%, positive likelihood ratio – 1.842, negative likelihood ratio – 0.482, positive predictive value – 0.462, negative predictive value – 0.812. The sensitivity of the test of GH secretion after falling asleep is too low with respect to the requirements for screening test. The ROC curve analysis showed 95% sensitivity for the screening test on the level of 19.0 ng/ml; however, with a very low specificity – below 25%, thus making this test completely useless as a screening procedure. [b]conclusions.[/b] The obtained results strongly contradict the opinion that the assessment of GH secretion after falling asleep should be a screening test in diagnosing GHD in children with short stature

Thyroid function in children with growth hormone (GH) deficiency during the initial phase of GH replacement therapy - clinical implications

BACKGROUND: Normal thyroid hormone secretion or appropriate L-thyroxine (L-T(4)) substitution is necessary for the optimal effect of the growth hormone (GH) administration on growth rate. The decrease of free thyroxine (FT(4)) levels at recombinant human GH (rhGH) therapy onset has been reported in several studies. The aim of the present study was to evaluate the effect of rhGH administration on thyrotropin (TSH) and FT(4 )serum concentrations in children with GH deficiency (GHD) during the 1st year of therapy, as well as to assess potential indications to thyroid hormone supplementation in them. PATIENTS AND METHODS: The analysis involved data of 75 children (59 boys, 16 girls) with disorders of GH secretion (GHD, neurosecretory dysfunction - NSD) and partial GH inactivity (inactGH), who were treated with rhGH for - at least - one year. In all the children, body height and height velocity (HV) were assessed before and after 1 year of therapy, while TSH, FT(4), IGF-I and IGFBP-3 before treatment and after 3-6 months and 1 year of treatment. In the patients, who revealed hypothyroidism (HypoT), an appropriate L-T(4 )substitution was introduced immediately. The incidence of HypoT, occurring during the initial phase of rhGH therapy, was assessed, as well as its influence on the therapy effectiveness. RESULTS: Before rhGH substitution, there were no significant differences in either auxological indices or TSH and FT(4 )secretion, or IGF-I concentration and its bioavailability among the groups of patients. During the initial 3-6 months of rhGH administration, a significant decrease of FT(4 )serum concentration, together with a significant increase of IGF-I SDS and IGF-I/IGFBP-3 molar ratio was observed in all the studied groups. In 17 children, HypoT was diagnosed and L-T(4 )substitution was administered. Despite similar IGF-I secretion increase, the improvement of HV presented significantly lower in children with HypoT than in those who remained euthyroid all the time. CONCLUSIONS: The incidence of HypoT during the initial phase of GH treatment in children with GHD and the negative effect of even transient thyroid hormone deficiency on the growth rate should be taken into account