Objectives The aim of this study was to investigate the biological variation of total thyroxine (T4), free T4 (fT4) and thyroid-stimulating hormone (TSH) in 11 clinically healthy cats aged between 3 and 15 years old, in Sydney, Australia. Methods Blood was collected weekly for up to 6 weeks and serum T4, fT4 and TSH concentrations were analysed using canine-specific reagents. Restricted maximum likelihood was used to estimate within-subject, between-subject and analytical variance components, which were recorded in terms of the related coefficients of variation. The index of individuality and reference change values were then calculated for each analyte. Results T4 and TSH had intermediate individuality, indicating both subject-based and population-based reference intervals (RIs) could be used, with the knowledge that population-based RIs are suboptimally sensitive. fT4 had high individuality, indicating subject-based RIs are more appropriate than population-based RIs. Conclusions and relevance This study has demonstrated that subject-based RIs could be more sensitive than population-based RIs for the diagnosis of thyroid dysfunction in cats.

Abstract. The aim of this study was to examine the hypothesis that follicular and uterine perfusion as well as endometrial gene expression during the ovulatory period differs after induction of luteolysis during the 1 st follicular wave compared with the 2 nd wave or in intact cycle. Nine healthy non-lactating Holstein-Friesian cows were examined during three estrous cycles. A prostaglandin F2α analogue (PGF) was administered randomly either on Day 7 (1 st wave cycle) or Day 11 (2 nd wave cycle) after detection of ovulation (=Day 1). No hormonal treatment was used in the intact cycle with spontaneous ovulation. Transrectal Doppler sonography was conducted daily after PGF injection and in the intact cycle beginning on Day 18 of the estrous cycle until ovulation. Follicular blood flow (FBF) was determined by measuring the maximum area of colour pixels on digitalized images of the follicles. Uterine blood flow was quantified by the time-averaged maximum velocity (UTAMV) and pulsatility index (PI) in both uterine arteries. Blood flow measurements were carried out on Days -1 and 0. Endometrial biopsy specimens were taken on Day 1 and analyzed for the gene expressions of estrogen, progesterone, oxytocin and VEGF receptors and eNOS and iNOS using RT-PCR. The interval from PGF injection to ovulation was shorter (P<0. [309][310][311][312][313][314][315] 2009) here are several reports about differences in the size and contents of follicles of the first and other follicular waves in cows [1][2][3][4]. Follicular fluid of the dominant follicle of the first follicular wave shows a higher concentration of estradiol than fluid of follicles of the second wave [2]. Furthermore, thecal cells from the dominant follicle of the first wave cultured in vitro secrete more progesterone than those of the dominant follicle of the second wave. Despite lower estradiol and progesterone concentrations, dominant follicles of the second wave are larger than those of the first wave [2]. However, the size of the dominant follicle is not an indicator of its functional status [3,4]. In cycling cows, angiogenesis, as determined by colour Doppler sonography, is a good parameter for evaluation of the functional status of the follicle. Follicular perfusion is markedly higher in dominant follicles than in subdominant follicles [5], and the walls of atretic follicles lack blood flow [6]. In a recent colour Doppler sonographic study, the vascularity of the preovulatory follicle was investigated in heifers before insemination. The results supported the hypothesis of a positive relationship between the extent of blood flow of the preovulatory follicle and successful establishment of pregnancy in cattle [7].The technique of colour Doppler sonography allows not only the determination of ovarian perfusion, but also measurement of uterine blood supply [8]. Although up to now only little information has been available in cows about changes in uterine blood flow during the estrous cycle [8] and pregnancy [9,10], a relationship between uterine perfusion and fe...