The aim of this study was to collect further data about levels of endogenous hormones in foodstuffs derived from animal production. Because of expected higher concentrations of especially estrogens in colostrum compared to other foodstuffs, our investigation focused on this matrix. For evaluation of endogenous steroid hormones in separated colostrum (fat and defatted fraction) and colostrum powder, the relevant free and conjugated estrogens (estradiol-17β, estradiol-17α, estrone, and estriol) androgens (androstendione, 19nor-androstendione, 19nor-testosterone-17β, 19nor-testosterone-17α, testosterone-17β, and testosterone-17α), and progesterone were determined by means of liquid chromatography-tandem mass spectrometry (LC-MS/MS). Upmost determined concentrations were found in the fat fraction, with 25.56 and 7.59 μg/L for estrone and androstendione, respectively. In defatted milk and colostrum powder, conjugated estrogens dominated, whereas total (free and conjugated) estrone (5.51 μg/L; 15.0 μg/kg) exceeded estradiol-17α (2.66 μg/L; 7.5 μg/kg) and estradiol-17β (2.28 μg/L; 3.3 μg/kg). Neither 19nor-steroids nor estriol were detected in colostrum fractions or processed colostrum.

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