Thyroid hormones in canine pregnancy and lactation

It is believed that thyroid function has a significant effect on fertility and fetal development in mammals. So far, however, only few studies have been published about potential effects of the reproductive cycle stage on thyroid hormone concentrations in dogs. Therefore, over the course of 122 pregnant and non-pregnant cycles in healthy bitches, Thyroid stimulating hormone (TSH), free Thyroxine (fT4), total Thyroxine (tT4) and Progesterone (P4) were measured six times to assess the influence of the cycle stage and pregnancy on hormone concentrations. The aim was to evaluate established reference intervals for the thyroid hormones in a female study population. Of the 122 bitches, 98 became pregnant. Blood samples were collected during estrus, three times in pregnancy, during lactation and after weaning, or at equivalent times during and after estrus in non-pregnant dogs. No differences between pregnant and non-pregnant animals in any of the thyroid hormones were found. Hormone concentrations, however, differed significantly between the six samplings (p < .01). TSH initially declined during pregnancy, then rose again. The mean concentration of all dogs exceeded the overall upper reference limit of 0.70 ng/mL during lactation. Concentrations of tT4 and ft4 increased during the first third of pregnancy and then subsequently declined. The overall reference limits for tT4 were 0.47-3.20 μg/dL, and for fT4 4.86-29.60 pmol/L, but the reference intervals varied between the sampling dates. The observed patterns may reflect that maternal tT4 and fT4 seem to have important effects during early pregnancy, including a pronounced negative feedback effect on TSH. The initial increase and subsequent decline of tT4 and fT4 concentrations during the course of pregnancy is in accordance with findings in humans and may support the development of fetal thyroid function. The observed peak of TSH concentrations during lactation suggests that the demand for thyroid hormones in this phase is largest. Even if the underlying causes and mechanisms of thyroid regulation are not fully understood, the results of this study show relevant changes of hormone concentrations in the course of the sexual cycle and pregnancy. In that regard, cycle stage needs to be considered when assessing thyroid function in bitches.

Diagnostic tests in canine andrology - What do they really tell us about fertility?

Dog breeders often require breeding soundness evaluations which include andrological examinations of the genital organs, hormone measurements, and semen analyses. During the past decades, a considerable number of research results have been published, allowing diagnoses of specific andrological conditions and fertility assessment. For specific examinations, however, no standard procedures have been defined and for some parameters different reference ranges have been published. Therefore, examination results from different facilities are difficult to compare and profound conclusions regarding health and fertility of a male dog are not always possible. Conventional semen examination, however, is still useful in identifying deviations or no deviations from normality, especially if confounding factors are taken into account and if the exam is repeated in case of inconclusive findings. A standardization of examination procedures and reference ranges would help to harmonize the exchange of examination results and interpretation of the findings.

Improving decision-making in complicated or rare cases-An approach towards Evidence-based Veterinary Medicine in small animal reproduction

The concepts of Evidence-based Veterinary Medicine (EBVM) provide a methodological and systematic approach to include the best evidence from research into clinical decision-making. These concepts include steps as the search and assessment of relevant research findings and consideration of individual aspects. In addition, owners and other persons involved in animal health care should be included in shared decision-making. Some breeders have good basic knowledge concerning breeding management and characteristics of diseases and concerning advantages and disadvantages of different therapeutic approaches, while others are notable to understand complex medical interrelations or emergency situations. All these aspects need to be addressed when communicating and discussing different diagnostic, prophylactic and therapeutic options. In special fields, such as small animal reproduction, veterinarians often see animals with rare diseases or complex conditions so that an application of standard therapies and well-established textbook recommendations is not possible. To learn more about cases too rare for successful systematic research, the case collection tool REPROCASES (www.evssar.org/reprocases) is now available. The aim of this project is to gather information from specialists on small animal reproduction in a multicentre approach. If you see rare or not well-investigated cases such as cystic ovarian diseases, cryptorchidism or others, you are more than welcome to share your findings via the database. Even if this approach cannot completely replace standardized clinical trials, the idea is to gather more information on effects, prognosis, side effects and long-term fertility for specific conditions.