Clinical endocrinology of thyroid gland function in ruminants

Abstract

After briefly introducing the basec steps in production and metabolism of thyroid hormones, the author gives an overview of nutritional, metabolic and disease related factors and endocrine interactions influencing thyroid gland function in ruminants, particularly in the postpartum dairy cow. Involvement of thyroid hormonal regulation of seasonal patterns of reproduction as well as ovarian endocrine function are discussed.Keywords: thyroxin; triiodothyronine; ovary; metabolism; ruminants Abbreviations: 5'D = 5'-deiodinase (syn.: outer-ring deiodinase); 5D = 5-deiodinase (syn.: inner-ring deiodinase); BHB = βOH-butyrate; E 2 = 17β-estradiol; FSH = follicle stimulating hormone; GH = growth hormone; GnRH = gonadotropin releasing hormone; hCG = human chorionic gonadotropin; IGF-I = insulin-like growth factor-I (syn.: somatomedin C); IL = interleukin; LH = luteinizing hormone; mRNA = messenger ribonucleic acid; NEB = negative energy balance; NEFA = non-esterified fatty acids; P 4 = progesterone; PVN = paraventricular nucleus of the hypothalamus; rT 3 = 3,3',5'-triiodothyronine (syn.: reverse-triiodothyronine); T 3 = 3,3',5-triiodothyronine; T 4 = thyroxine; TNFα = tumor necrosis factor-α; TRH = thyrotropin-releasing hormone; TSH = thyroid-stimulating hormone (syn.: thyrotropin)

Relationshipis Between Blood Hormones and Metabolites in Simmental Dairy Cows During Transition Period and Mid Lactation

“…Blood levels of thyroid hormones T3 (p<0.05) and T4 (p>0.05) in Group 1 (late pregnancy) and Group 2 (early lactation) were significant lower compared with Group 3 (mid lactation). These results are comply with other authors (Aceves et al, 1985;Jindal and Ludri, 1994;Tiirats, 1997;Huszenicza et al, 2002;Djoković et al, 2007) suggesting that concentration of thyroid hormones are changes as a result of adaptation process of high energy demand of udder and it could be reason for metabolic disorders. During early stage of lactation blood NEFA and BHB were significantly higher (p<0.05) than in late pregnancy and mid lactation cows.…”

“…Thyroid hormones, primarily triiodothyronine (T3), play an important role in the regulation of energy metabolism. A decrease in thyroid hormone levels occurs in the blood of peripartal cows, particularly during early lactation, when body reserves are mobilized for the production of high amounts of milk (Bonczek et al, 1988;Tiirats, 1997;Huszenicza et al, 2002). NEB, lipomobilization and hypothyreoidism at the onset of lactation in Simmental cows are accompanied with tremendous changes in energy metabolism and oxidation processes, particularly in liver cells.…”

Induction of Twinning in Noemi Ewes Using Two Protocols of a Recombinant Human Follicle Stimulating Hormone Versus Porcine Pituitary-Derived FSH and their Subsequent Impacts on Maternal Hormones

“…Regarding thyroid hormones (T3 and T4), the highest level of T3 in the blood was found in ewes given a single dose of human FSH. There are several studies in the literature reporting on the relationship between thyroid hormones and reproduction (33). It has been previously documented that T3 and T4 directly change the steroidogenic capacity of porcine and human granulosa cells.…”

Hormonal changes in dairy cows during periparturient period

“…In cows exhibiting postpartum negative energy balance, lower concentrations of T3 and T4 hormones was noted. Low levels of these hormones were observed during the first three months of lactation, due to the fact that the concentration of T3 and T4 is negatively correlated with milk productivity [Capuco et al 2001, Huszenicza et al 2002, Jorritsma et al 2003, Klimienė et al 2008, Djoković et al 2010. According to Meikle et al [2004] in the period from 30 days before to 60 days after calving a higher concentration of T3 in multiparous Holstein cows (0.89 ng • ml -1 ) compared to primiparous (0.8 ng • ml -1 ) was noted.…”