The Mechanism of the T3 Response to Parturition

Sack, Joseph; Beaudry, M; DeLamater, Paul V.; Oh, William; Fisher, D.

doi:10.1203/00006450-197508000-00094

Cited by 6 publications

(3 citation statements)

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“…In agreement with the results of Sack et al (1975), this suggests that the increase in plasma T3 levels was not a result of neonatal TSH hypersecretion. However, no convincing explanation has been reported and an hypothetical 5'-deiodinase activation has not been proved yet.…”

Section: Introductionsupporting

confidence: 80%

Effects of food restriction on cortisol, TSH and iodothyronine concentrations in the plasma of the newborn lamb

Wrutniak¹,

Cabello²

1987

Reprod. Nutr. Dévelop.

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Summary. The influence of food restriction, applied from birth to 36 h post partum, on neonatal thyroid function was studied in newborn Limousin x Romanov lambs. The control animals (n = 18) had free access to the mother and suckled ad libitum. Restricted lambs (n = 16) were removed from the mother and received limited amounts of colostrum in proportion to birth weight ; 8 lambs were supplemented with lactose (30 g/I of colostrum).Plasma glucose and free fatty acid levels were significantly lower in restricted lambs, whereas urea levels were elevated. Plasma cortisol concentrations in control animals decreased during the period studied, but rose during the first 8 h of life in restricted lambs. Lactose supplementation only partially restored glucose and urea levels. Food restriction induced considerable modifications in neonatal thyroid function. The postpartum rise in plasma thyroid-stimulating hormone (TSH), thyroxine (T4) and free T4 levels occurring in control lambs was inhibited in restricted animals. However, the surge in plasma triiodothyronine (T3) levels was not affected, suggesting that this change was not related to physiological neonatal TSH hypersecretion. Thereafter, thyroid hormone concentrations decreased sharply during food restriction, whereas reverse T3 levels remained higher than in the controls. In response to these T4 and T3 deficiencies, plasma TSH levels rose only in lactose-supplemented animals.In agreement with the significant modifications in the values of the T3/free T4 and reverse T3/free T4 ratios, the abrupt changes in T3 and reverse T3 levels suggest that food restriction affected the peripheral conversion of T4 into T3 and reverse T3.Twelve hours after the onset of refeeding, plasma T4 and reverse T3 levels were restored, but not the T3 levels ; this agrees with results obtained in other animals.In conclusion, food restriction strongly affected neonatal thyroid function in lambs in terms of secretion and peripheral T4 conversion.Introduction.

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Section: Introductionsupporting

confidence: 80%

Effects of food restriction on cortisol, TSH and iodothyronine concentrations in the plasma of the newborn lamb

Wrutniak¹,

Cabello²

1987

Reprod. Nutr. Dévelop.

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“…The conversion ofT4 to rT3 and T3 is not TSH dependent. The patterns observed suggest that peripheral enzymatic pathways for thyroxine metabolism rapidly mature in the newborn infant, probably via autonomic activation of the thyroxine hydroxylase activity (Fisher, 1975;Sack et al, 1975b). By 1-2 weeks, the pattern of serum thyroid hormones is similar to that of adults.…”

Section: Perinatal Secretion Of Thyroid Hormonesmentioning

confidence: 85%

Human Growth

1986

107

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“…Hormonal changes have also been studied in ewes and lambs (5, 13). The T., increase seen a few minutes after birth may be produced when the maternal cord is cut (18).…”

mentioning

confidence: 99%

Iodoprotein and Iodoamino Acid Distribution in Pig Thyroid Tissues at Different Periods of Development

Etling¹,

Gehin²

1977

Neonatology

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A biochemical study of the thyroid tissue in pigs at various stages of development was undertaken. The iodine and protein concentrations, and the iodoamino acid content of thyroglobulin (TG) were determined. Expressed as μg ¹²⁷I/100 mg wet tissue, the mean iodine content of pig fetus is 66.4, 89.2 in the piglet and 168 in the adult pig. TG accounts for 95% of total proteins; its content increases with age. Mean iodine content of TG is 0.70 μg ¹²⁷I/100 μg in the fetus, 0.78 in the piglet and 0.97 in the adult pig. The average number of molecules of thyroxine residues is 1.6 in the fetus, 2.2 in the piglet and 3.5 in the adult. Average triiodothyronine residues are lower around birth than in the adult. At all stages of development, synthesis of thyroxine is less effective in the pig than in the human, relative to the iodine content of TG. In contrast to the human, iodinated compounds are not found at a very low level near birth, but TG and iodine content regularly increase.

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The Mechanism of the T3 Response to Parturition

Cited by 6 publications

References 0 publications

Effects of food restriction on cortisol, TSH and iodothyronine concentrations in the plasma of the newborn lamb

Effects of food restriction on cortisol, TSH and iodothyronine concentrations in the plasma of the newborn lamb

Human Growth

Iodoprotein and Iodoamino Acid Distribution in Pig Thyroid Tissues at Different Periods of Development

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