Rates of standard metabolism (SMR) are highly variable among individuals within vertebrate populations. Because SMR contributes a substantial proportion of an individual's energy budget, among-individual variation in this trait may affect other energetic processes, and potentially fitness. Here, we examine three potential proximate correlates of variation in SMR: organ mass, serum T4 thyroxine ...

Background: The secretion of thyroxine (T4) as the main hormone of thyroid gland is regulated by androgens. The present study aimed to evaluate the effect of testosterone and finasteride administration and castration on serum levels of T4 and to show the effect of this regulation on total body weight, weight of testis, and the weight of prostate. Methods: Male adult rats (n = 32) were divided i...

One of the most clearly defined endocrine changes during the parr-smolt transformation of anadromous salmonids is an increase in plasma levels of thyroid hormones. The role of pineal hormone melatonin in timing and synchronisation of smoltification is widely discussed. The effect of administration of exogenous thyroxine (T4) on plasma melatonin was investigated in juvenile Atlantic salmon (Salm...

Objective: Knowing the ideal levels of triiodothyronine (T3), thyroxine (T4), FT3, FT4, and thyrotropin-stimulating hormone (TSH) for each pregnancy trimester are goal. Methods: The Department Obstetrics Gynecology at Pacific Institute Medical Sciences in Udaipur treated 150 patients (obstetric cases) current longitudinal research. following parameters were examined a fasting blood sample: T3, ...

the aim of this study was to evaluate total iodine, triiodothyronine (t3) and thyroxine (t4) status in the blood serum of holstein cows on six farms in central iran. total iodine, t3 and t4 concentrations were measured in 90 blood serum samples (15 per farm). mean concentrations of total iodine (38.80 ± 1.52 µg/l) and t3 (1.57 ± 0.10 nmol/l) were lower but the mean concentration of t4 (45.60 ± ...

Woodchucks ( n = 12-14/group) with circannual cycles entrained to northern versus southern hemisphere photoperiods were assessed monthly for 16 mo. Changes in serum total triiodothyronine (TT3), free thyroxine (T4), total thyroxine (TT4), and prolactin were determined in a subset of five animals per group. Metabolic hormone results were examined in relation to changes in body weight, food intak...

Hypothyroidism, defined as thyrotropin (TSH) above and free thyroxine (fT4) serum level below the reference rage, as well as hyperthyroidism, defined as suppressed TSH and elevated thyroid hormones exceeding the upper limit of the reference range, may have major impacts on fertility and pregnancy outcome. Ideally, euthyroidism, defined as TSH and fT4 in the reference range, should be establishe...