Serum Precipitable Iodine Concentrations During Pregnancy 1

Heinemann, Martin; Johnson, Carl E.; Man, Evelyn B.

doi:10.1172/jci101928

Cited by 117 publications

(36 citation statements)

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“…Since pregnancy and estrogen administration produce increases in PBI and TBP in the serum, it appears possible that similar alterations might occur in women during the menstrual cycle. Attempts to detect such changes in the PBI revealed no unequivocal cyclic variation (5,38). In the nonpregnant subjects who served as controls for the present study, no significant differences between TBP in men and women were observed (15), but the time of sampling was not correlated with the menstrual cycle.…”

Section: Discussioncontrasting

confidence: 57%

“…The thyroid gland may become enlarged and hyperplastic (1,2), thyroidal uptake of radioiodine is increased (3,4), "conversion" of blood iodide to organic form is more rapid (4), and the serum proteinbound iodine (PBI) is elevated (5,6). Although these alterations are like those seen in hyperthyroidism, they appear to be associated, in early pregnancy at least, with an unequivocally euthyroid state.…”

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confidence: 99%

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Thyroxine-Binding by Serum Protein in Pregnancy and in the Newborn

Robbins¹,

Nelson²

1958

J. Clin. Invest.

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Thyroid structure and function in man undergo a number of changes during pregnancy. The thyroid gland may become enlarged and hyperplastic (1, 2), thyroidal uptake of radioiodine is increased (3, 4), "conversion" of blood iodide to organic form is more rapid (4), and the serum proteinbound iodine (PBI) is elevated (5, 6). Although these alterations are like those seen in hyperthyroidism, they appear to be associated, in early pregnancy at least, with an unequivocally euthyroid state. Whereas the PBI rises as early as the first or second month of gestation, and remains at about the same level throughout pregnancy, elevation of the basal metabolic rate (2, 7) begins in the latter half of pregnancy and rises progressively. Circulatory changes, such as increased cardiac output (8), may precede the rise in oxygen consumption but these also change progessively until shortly before term.It has been postulated that alterations in the interaction of thyroid hormone with serum proteins might provide an explanation for these paradoxical findings (6). Inasmuch as circulating thyroxine is largely bound to what appears to be a specific alpha globulin (TBP) (9, 10), attention has been directed toward this protein in pregnancy. It has been demonstrated that TBP in pregnancy has an increased ability to complex thyroxine (10-13).In the present study, the thyroxine-binding capacity of TBP has been quantitated during the course of normal pregnancy and in newborn infants. From these data it has been possible to calculate an approximate concentration of free thyroxine in the serum of these subjects. METHODSSerum was obtained from 16 women during and after uncomplicated pregnancies, usually after an overnight fast, from umbilical vein blood sampled at delivery in three subjects, and from external jugular venipuncture in two infants on the third day after delivery. Mixtures of serum with I13'-labeled L-thyroxine 1 were prepared according to the procedure described previously (14). Prior to use, each of the eight thyroxine preparations employed was tested for radiochemical purity by chromatography, and was repurified, when necessary, to a purity of 90 per cent or better by an extraction procedure (15). Iodine analyses2 were performed by a modification of the method of Zak, Willard, Myers, and Boyle (16). The thyroxine-serum mixtures were subjected to zone electrophoresis on filter paper strips, using barbital buffer, pH 8.6, ionic strength 0.1, and a "reverse-flow" technique (15). This modification of the electrophoresis procedure avoided the inclusion of albumin-bound thyroxine in the alpha globulin zone.For measurement of the thyroxine-binding capacity of TBP, the quantity of thyroxine added to each serum was sufficient to effectively saturate the thyroxine-binding sites on TBP. Actual saturation of these sites is approached asymptotically (15). Analysis of data obtained with normal sera (10), however, had indicated that the amount of thyroxine associated with alpha globulin reaches an effective plateau when less than 60 per cent of t...

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Section: Discussioncontrasting

confidence: 57%

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confidence: 99%

Thyroxine-Binding by Serum Protein in Pregnancy and in the Newborn

Robbins¹,

Nelson²

1958

J. Clin. Invest.

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“…In 1948 it was reported by Heinemann, Johnson and Man (1) that early in pregnancy the precipitable (protein-bound) iodine in the serum (SPI) rose to concentrations in the upper range of normal or even to levels that outside of pregnancy are characteristic of hyperthyroidism. It also appeared that if the SPI did not rise, the pregnancy was likely to end in abortion within the first four months.…”

mentioning

confidence: 99%

The Precipitable Iodine of Serum in Normal Pregnancy and Its Relation to Abortions 1

Man¹,

Heinemann²,

Johnson³

et al. 1951

J. Clin. Invest.

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In 1948 it was reported by Heinemann, Johnson and Man (1) that early in pregnancy the precipitable (protein-bound) iodine in the serum (SPI) rose to concentrations in the upper range of normal or even to levels that outside of pregnancy are characteristic of hyperthyroidism. It also appeared that if the SPI did not rise, the pregnancy was likely to end in abortion within the first four months. Some evidence was presented that such accidents might be prevented by the administration of active thyroid substance. The present paper deals with a further investigation of the phenomenon.

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“…However, although other objective determinations of thyroid function such as the measurement of the basal metabolic rate or the lipids of the serum are unreliable in acute hepatitis, none of these patients had clinical evidences of hyperthyroidism nor was the course suggestive of this disease. High values of SPI are found also in pregnancy (14), but the cause of the rise in the two conditions seems to be dissimilar inasmuch as the rise occurs in hepatitis only early in the course and is not related to the severity of the disease.…”

Section: Discussionmentioning

confidence: 91%