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Peripheral thyroid hormone levels and hepatic thyroid hormone deiodinase gene expression in dairy heifers on the day of ovulation and during the early peri-implantation period

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ABSTRACT

Background: Before the onset of fetal thyroid hormone production, the transplacental delivery of maternal thyroid hormones is necessary for embryonic and fetal development. Therefore, the adaptation of maternal thyroid hormone metabolism may be important for pregnancy success and embryo survival. The aims of this study were to determine the thyroid hormone levels during the early peri-implantation period until day 18 and on the day of ovulation, to determine whether pregnancy success is dependent on a “normothyroid status” and to determine whether physiological adaptations in maternal thyroid hormone metabolism occur, which may be necessary to provide sufficient amounts of biologically active T3 to support early pregnancy. Therefore, blood samples obtained on the day of ovulation (day 0) and days 14 and 18 of the Holstein–Friesian heifers (n = 10) during the respective pregnant, non-pregnant and negative control cycles were analyzed for thyroid-stimulating-hormone (TSH), thyroxine (T4) and triiodothyronine (T3). Liver biopsies (day 18) from pregnant and respective non-pregnant heifers were analyzed for mRNA expression of the most abundant hepatic thyroid hormone deiodinase (DIO1) by real time qPCR.

Results: Although liver DIO1 mRNA expression did not differ between the pregnant and non-pregnant heifers on day 18, the serum concentrations of TSH and T3 on day 18 were higher in non-pregnant heifers compared to pregnant heifers (P < 0.05). Moreover, T3 decreased between day 0 and 18 in pregnant heifers (P < 0.001).

Conclusions: In conclusion, no associations between thyroid hormone patterns on day 18 and pregnancy success were detected. During the early peri-implantation period, TSH and T3 may be affected by the pregnancy status because both TSH and T3 were lower on day 18 in pregnant heifers compared to non-pregnant dairy heifers. In further studies, the thyroid hormone axis should be evaluated throughout the entire gestation to confirm these data and identify other possible effects of pregnancy on the thyroid hormone axis in cattle.

No MeSH data available.


Age adjusted A thyroid-stimulating-hormone (∆TSH), B thyroxine (∆T4) and C triiodothyronine (∆T3) blood concentrations (mean ± SEM) of pregnant (p) heifers and respective non-pregnant (np) and negative control cycles (NC); the significant differences between the groups on certain days are marked with different letters. The results of the mixed–model are shown in the table below each graph
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Fig1: Age adjusted A thyroid-stimulating-hormone (∆TSH), B thyroxine (∆T4) and C triiodothyronine (∆T3) blood concentrations (mean ± SEM) of pregnant (p) heifers and respective non-pregnant (np) and negative control cycles (NC); the significant differences between the groups on certain days are marked with different letters. The results of the mixed–model are shown in the table below each graph

Mentions: The age effect components in the linear mixed-effect model were estimated with the following intercepts and slopes: TSHest(age) = 8.1496–0.01016*age (P < 0.001), T4est(age) =−2.1811 + 0.08157*age (P = 0.019), T3est(age) = 0.7432 + 0.001949*age P = 0.017). The results throughout the manuscript are presented as mean ± standard error of the mean (SEM). Concerning T4, T3 and TSH concentrations, data was adjusted according to the linear regression component of the model (age). Therefore, differences were formed: “hormone concentration at each data point” minus “estimated concentration at age at sample day” resulting in “∆ hormone concentrations” (Fig. 1). Hepatic mRNA expression was compared using a paired Student’s t test (PROC TTEST PAIRED) and results are presented as mean ± SEM as well. For all procedures, the statistical significance was pre-established at P < 0.05. P values between P > 0.05 and P < 0.10 were considered statistical tendencies. F and P values for the fixed effects are presented below each graph (Fig. 1), significant differences between pregnant (p) negative control (NC), and non-pregnant (np) cycles are indicated by different letters (Fig. 1) whereas differences along the time points within each group are described in the text.Fig. 1


Peripheral thyroid hormone levels and hepatic thyroid hormone deiodinase gene expression in dairy heifers on the day of ovulation and during the early peri-implantation period
Age adjusted A thyroid-stimulating-hormone (∆TSH), B thyroxine (∆T4) and C triiodothyronine (∆T3) blood concentrations (mean ± SEM) of pregnant (p) heifers and respective non-pregnant (np) and negative control cycles (NC); the significant differences between the groups on certain days are marked with different letters. The results of the mixed–model are shown in the table below each graph
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5017029&req=5

Fig1: Age adjusted A thyroid-stimulating-hormone (∆TSH), B thyroxine (∆T4) and C triiodothyronine (∆T3) blood concentrations (mean ± SEM) of pregnant (p) heifers and respective non-pregnant (np) and negative control cycles (NC); the significant differences between the groups on certain days are marked with different letters. The results of the mixed–model are shown in the table below each graph
Mentions: The age effect components in the linear mixed-effect model were estimated with the following intercepts and slopes: TSHest(age) = 8.1496–0.01016*age (P < 0.001), T4est(age) =−2.1811 + 0.08157*age (P = 0.019), T3est(age) = 0.7432 + 0.001949*age P = 0.017). The results throughout the manuscript are presented as mean ± standard error of the mean (SEM). Concerning T4, T3 and TSH concentrations, data was adjusted according to the linear regression component of the model (age). Therefore, differences were formed: “hormone concentration at each data point” minus “estimated concentration at age at sample day” resulting in “∆ hormone concentrations” (Fig. 1). Hepatic mRNA expression was compared using a paired Student’s t test (PROC TTEST PAIRED) and results are presented as mean ± SEM as well. For all procedures, the statistical significance was pre-established at P < 0.05. P values between P > 0.05 and P < 0.10 were considered statistical tendencies. F and P values for the fixed effects are presented below each graph (Fig. 1), significant differences between pregnant (p) negative control (NC), and non-pregnant (np) cycles are indicated by different letters (Fig. 1) whereas differences along the time points within each group are described in the text.Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Background: Before the onset of fetal thyroid hormone production, the transplacental delivery of maternal thyroid hormones is necessary for embryonic and fetal development. Therefore, the adaptation of maternal thyroid hormone metabolism may be important for pregnancy success and embryo survival. The aims of this study were to determine the thyroid hormone levels during the early peri-implantation period until day 18 and on the day of ovulation, to determine whether pregnancy success is dependent on a &ldquo;normothyroid status&rdquo; and to determine whether physiological adaptations in maternal thyroid hormone metabolism occur, which may be necessary to provide sufficient amounts of biologically active T3 to support early pregnancy. Therefore, blood samples obtained on the day of ovulation (day&nbsp;0) and days 14 and 18 of the Holstein&ndash;Friesian heifers (n&nbsp;=&nbsp;10) during the respective pregnant, non-pregnant and negative control cycles were analyzed for thyroid-stimulating-hormone (TSH), thyroxine (T4) and triiodothyronine (T3). Liver biopsies (day&nbsp;18) from pregnant and respective non-pregnant heifers were analyzed for mRNA expression of the most abundant hepatic thyroid hormone deiodinase (DIO1) by real time qPCR.

Results: Although liver DIO1 mRNA expression did not differ between the pregnant and non-pregnant heifers on day&nbsp;18, the serum concentrations of TSH and T3 on day&nbsp;18 were higher in non-pregnant heifers compared to pregnant heifers (P&nbsp;&lt;&nbsp;0.05). Moreover, T3 decreased between day&nbsp;0 and 18 in pregnant heifers (P&nbsp;&lt;&nbsp;0.001).

Conclusions: In conclusion, no associations between thyroid hormone patterns on day 18 and pregnancy success were detected. During the early peri-implantation period, TSH and T3 may be affected by the pregnancy status because both TSH and T3 were lower on day 18 in pregnant heifers compared to non-pregnant dairy heifers. In further studies, the thyroid hormone axis should be evaluated throughout the entire gestation to confirm these data and identify other possible effects of pregnancy on the thyroid hormone axis in cattle.

No MeSH data available.