Amniotic Fluid 3,3′- and 3f,5′-Diiodothyronine in Fetal Hypothyroidism in Sheep*

Maternal Thyroid Function is the Major Determinant of Amniotic Fluid 3,3′,5′-Triiodothyronine in the Rat

“…As in experiment 1, AF rT3 was normal in the FH group and markedly decreased in the MH and MFH groups. Unlike experiment 1, where AF rT3 was undetectable in these latter two groups, AF rT3 was detectable and significantly higher in the MH as compared with the MFH rats (MH, 13.5+0.8 vs. MFH, 8.4±+0.9, P < 0.05). …”

“…In 1975 Chopra and Crandell (2) observed that amniotic fluid (AF) 3,3',5'-triiodothyronine (reverse T3, rT3)1 concentrations were easily detectable during human pregnancy, in contrast to low or undetectable concentrations of thyroxine (T4) and 3,3',5'-triiodothyronine (T3). These observations have been confirmed by others (3)(4)(5)(6) and aroused considerable interest, suggesting that AF rT3 measurements might be a useful means of diagnosing fatal hypothyroidism in utero (7,8). ' Abbreviations used in this paper: AF, amniotic fluid; BW, body weight; C group, control group; FH group, fetal hypothyroidism group; LID, low-iodine diet; MFH group, combined maternal-fetal hypothyroidism group; MH group, maternal hypothyroidism group; MMI, methimazole; rT3, reverse T3; T3, 3,3',5-triiodothyronine; T4, thyroxine; TSH, thyrotropin; Tx, thyroidectomized.…”

“…The ovine species was not chosen for these studies since term AF rT3 concentrations are low in the sheep (8). Previously published rat (9)(10)(11)(12)(13)(14)(15)(16)(17) and primate (18,19) models of fetal hypothyroidism were not used since hypothyroidism had been induced at birth rather than in the fetus or combined maternal-fetal hypothyroidism resulted from the treatment regimen.…”

Amniotic and allantoic fluid concentrations of thyroxine, 3,3′,5′-tri-iodothyronine, 3,3′-di-iodothyronine and 3′,5′-di-iodothyronine in the pig during the period of gestation

“…A significant increase in AF T4 level, observed at mid-gestation (Table 1), coincided well with the begin¬ ning of fetal thyroid gland function. A relatively stable AF T4 concentration in the pig, during the second half of pregnancy, was comparable with that in the human (Morley et al 1979, Cooper et al 1982 but not compar¬ able with that in the sheep (Chopra et al 1979) or the rat (El-Zaheri et al 1981).…”

“…When this possibility was evaluated in pregnant sheep, it was found that the AF rT3 concentration was unexpectedly low as compared with both maternal and fetal serum. The ratio, mean AF rT3 to mean cord serum rT3 at term, was found to be about 0-023 in sheep (Chopra et al 1979 Our recent investigations (Slebodzinski & Brzezinska-Slebodzinska 1994) have revealed that the pattern of serum concentrations of T4, T3 and rT3 in the fetal pig differs markedly from that found in fetal sheep near term. Fetal serum T4 is much higher and T3 comparable or higher whereas rT3 concentrations are lower by about 60% ofthat in maternal serum.…”