Reference ranges for thyroid hormones in normal Italian children and adolescents and overweight adolescents.

BACKGROUND: As thyroid hormones are essential for normal pubertal growth and sexual development, TSH, free T3 (FT3) and free T4 (FT4) levels undergo progressive modification during childhood and puberty. AIM: To establish thyroid hormone reference ranges in pre-pubertal children, pubertal adolescents, and adults and to evaluate any differences in thyroid function between overweight and normalweight pubertal subjects. SUBJECTS AND METHODS: Chemiluminescent microparticle immunoassay was used to analyze TSH, FT3 and FT4 concentrations in serum samples from 508 children and adolescents aged 6 to 18 yr and 100 healthy adults aged 30 to 60 yr, and from 68 overweight pubertal adolescents. As data were not normally distributed, we compared them through non-parametric tests for independent samples and the reference ranges were assumed to lie between the 2.5th and 97.5th percentile. RESULTS: We found a progressive and significant reduction in TSH, FT3, and FT4 levels in the three groups with increasing age. TSH levels were significantly higher in overweight patients than in the normal-weight group, but there were no significant differences for FT3 or FT4. CONCLUSIONS: This study revealed significant differences in levels of thyroid hormone between different age groups and allowed us to establish normal reference ranges for pre-pubertal children between 0.87-5.19 mIU/l for TSH, 4.75-8.59 pmol/l for FT3, and 13.09-20.61 pmol/l for FT4, and for pubertal adolescents between 0.76- 4.51 mIU/l for TSH, 4.26-8.46 pmol/l for FT3 and 10.94-19.09 pmol/l for FT4.

Fluorescence quenching of dipyridamole associated to peroxyl radical scavenging: a versatile probe to measure the chain breaking antioxidant activity of biomolecules.

Dypiridamole is a highly efficient chain breaking antioxidant (Iuliano et al., Free Radic. Biol. Med. 18 (1995) 239-247) with an aromatic ring system responsible for an intense absorption band in the 400-480-nm region and for an intense fluorescence. Dipyridamole fluorescence is quantitatively quenched upon reaction with peroxyl radicals. In the presence of a flux of peroxyl radicals generated by thermal dissociation of azo-initiators, dipyridamole fluorescence decays linearly, showing a first-order reaction with respect to peroxyl radicals, and zero-order with respect to dipyridamole. The pH optimum for the fluorescence quenching is in the 7-8 range, from pH 7 to 6, the decay of fluorescence rapidly decreases to became negligible below pH 5.5. Dipyridamole consumption is blocked in the presence of an added chain breaking antioxidant for a time that is proportional to the antioxidant concentration. This effect is shown for ascorbic acid, trolox, vitamin E, uric acid, and N, N'-diphenyl-p-phenylenediamine. The slope of the linear correlation relative to trolox allows calculation of the bimolecular rate constant for a given molecule and peroxyl radicals. Comparison of data obtained by the dipyridamole consumption are comparable to values obtained by the oxygen consumption method.