Maternal Thyroid Research Articles

Effects of thyrotropin-releasing hormone (TRH) in maternal, fetal and newborn rats.

The effects of synthetic TRH and methyl TRH (pGlu-N3imMe-His-Pro-NH2) in maternal, fetal and newborn rats were investigated. Colloid droplet (CD) formation in the thyroid cell was enumerated as the index of thyroid hormone secretion induced by TSH. TSH concentration in the serum and pituitary was measured by a homologous radioimmunoassay of rat TSH. 10 fig TRH injected into the maternal tail vein increased the CD in the maternal thyroid from 12⁄25 follicles (control) to 442 μ 20⁄25 (SE) and in the 21 day fetal thyroid from 1⁄25 to 129 μ 12⁄25. 1 μg methyl TRH injected iv to the mother also increased CD in the maternal thyroid and fetal thyroid to 754⁄25 and 76⁄25, respectively. TSH injected to the mother stimulated maternal CD and did not affect the fetal CD. TSH levels in maternal serum at 30 min after administration of 10 μg TRH or 1 μg methyl TRH increased from 20 μU⁄ml to 442 nU⁄ml and 382 μU⁄ml, respectively. Administration of 10 pig TRH to the mother did not cause significant depletion of the pituit...

Maternal Iodine Status and Thyroid Function during Pregnancy

Background: Pregnant ladies are most likely to develop relative iodine deficiency during pregnancy to affect thyroid function in our population unless specific dietary care or therapeutic iodine supplementation is taken into account which is yet to be materialized. Methods: In this cohort study sixty uncomplicated normal pregnant women were enrolled in 1st trimester and followed up till delivery. In every trimester maternal iodine status & thyroid status were determined by urinary iodine & serum thyroid hormone concentration respectively. Results: Women progressively become more iodine deficient & tends to be hypothyroid as pregnancy advances. At 3rd trimester of pregnancy maternal Urinary Iodine found to be negatively correlated with their serum TSH. Conclusion: During pregnancy women develop iodine deficiency which adversely affects the thyroid function. So adequate iodine monitoring and iodine nutrition during pregnancy is necessary. Keywords: Urinary iodine level, TSH, FT3, FT4. doi: 10.3329/jom.v10i2.2815 J MEDICINE 2009; 10 : 56-59

Thyroid effect on birthweight in C57 BL mice and Peromyscus.

SummaryThyroxine and/or propyl-thiouracil were administered to pregnant C 57 BL mice, Peromyscus maniculatus and P. polionotus to alter the thyroid hormone titer. No significant differences in birthweight were observed between offspring from mothers receiving either thyroxine in excess of the normal secretion rate or receiving thiouracil treatment contrasted with controls. Sub-toxic levels of maternal or fetal thyroid hormone appear to have no marked effect on neonatal weight in these rodents.The technical assistance of James Kelly is gratefully acknowledged.

Metabolism of Oral Iodide and 3,5-Diiodosalicylic Acid in the Pregnant Cow

Three near-term pregnant cows were studied. Two of these were each given simultaneous oral tracer doses of I131 as 3.5-diiodosalicylic acid (DI131S) and I125. The third cow was given both radioisotopes as iodide. One was sacrificed at 144 and two at 168 hr after dosage. For the animals given DI131S, the percentage of dose of each isotope excreted (urinary and fecal) in 144 hr was I131, 83.6%; I125, 43.1%. The average percentage of the dose in the thyroids at the time of sacrifice was I131 in the maternal thyroid, 2.3%; I131 in the fetal a thyroid, 2.1%; I125 in the maternal thyroid, 18.0%; I125 in the fetal thyroid, 15.9%. Iodine fed as DIS was not as available to either maternal or fetal thyroid and did not cross the placenta as readily as iodine fed as iodide. The animal given both isotopes as iodide exhibited no differences between the two isotopes in excretion or in concentrations in the various tissues.

I-131 DOSE TO HUMAN THYROIDS IN NEW YORK CITY FROM NUCLEAR TESTS IN 1962.

Abstract—During the U.S. and U.S.S.R. nuclear weapons tests in 1962, the I131 content was measured in 456 human thyroids dissected at autopsies of New York residents with no known history of thyroid disease. Measurements were also made of thirty-one fetal thyroids, including five cases in which the maternal thyroids were also available for post-mortem study. In addition, in vivo measurements were made of the uptake of I131 in eleven normal adults who consumed known amounts of fresh milk contaminated with I131 from the weapons tests. Daily measurements of the milk distributed in New York City revealed that the average concentration of I131 was 38 pc/l. during the period from May 19, when this nuclide was first detected in the city, until January 5, 1963, when the study was discontinued. The maximum concentration was 370 pc/l. late in September. The most heavily exposed members of the population of New York City, based on measurements of dissected thyroids, received a thyroid dose of 40 mrad as a result of the 1962 nuclear tests. During a comparable period of time, in vivo measurements of adults who were consuming an average of 0.82 1. fresh milk/day disclosed the mean thyroid burden in the group to be 300 ± 130 pc compared to a mean of 88 ± 74 pc for the dissected thyroids during the same period. Although the latter thyroids were shown to contain less I131, on the average, than the in vivo cases selected from relatively heavy milk drinkers, the Medical Examiner's cases gave higher I131 values than hospital cases that came to autopsy. Using the measured values of I131 in milk as a basis of calculation, it is estimated that a child whose thyroid weighs 2 g and who consumes 1 l. milk/day received a dose of 140 mrad during the period covered by this study. The highest concentration of I131 in the thyroids of this series was 630 pc/g in a 20-mg thyroid from a 3-month fetus.

Radioiodine concentration by the fetal mouse thyroid.

Twenty-four hours following subcutaneous injection of radioiodine into pregnant mice various fetal and maternal tissues were removed, weighed and their radioactivity measured. Measurements at various days of gestation show the fetal mouse thyroid first concentrates iodine between the 14th and 15th days of gestation in mice with an average gestational period of 19 days. Development of the ability to concentrate iodine precedes bymore than a day the formation of follicles and colloid in the gland. As the iodine uptake of the litter increases greatly toward term, there is indication of a corresponding decrease in the iodine uptake by the maternal thyroid. Near term, the concentration of iodine in fetal thyroids and the total uptake by thyroids of whole litters equals or exceeds the concentration, in and uptake by, the maternal thyroid. It is suggested that changes in the placenta in mass and in capacity to concentrate and transmit iodine, particularly between the 17th and 18th days, may affect the iodine con...

Maternal and Foetal Thyroid

Maternal and Foetal Thyroid

Effect of destruction of thyroid tissue by radioactive iodine on reproduction in mice.

SUMMARY The effect of complete destruction of the thyroid gland by radioactive iodine on reproduction in the female mouse has been examined in detail. Possible direct effects of radiation on reproduction were differentiated from those due to thyroid destruction. Destruction of the thyroid tissue in the male mouse had no effect on fertility. In the thyroid-deficient female both fertility and litter frequency were unaffected, but the oestrous cycle was prolonged and the duration of 46% of gestations was longer than normal. There was a general shift in the distribution of litter size towards small litters in the thyroid-deficient group which reduced the average number of young per litter. Lactation, as judged by the weight of the offspring at weaning, was not affected by complete absence of the maternal thyroid gland. After weaning the growth rate of offspring of either sex from both thyroid-deficient and normal mothers was the same. Although the pituitary glands were enlarged in all the thyroid-deficient animals examined, tumours were not observed.

FETAL AND MATERNAL ATHYROSIS. II

The author has described a thyroid disturbance (1) that is prevalent among new-born domestic animals in western sections of this continent. The disease is one which affects swine, sheep, cattle, horses, goats and dogs, and occurs among such a wide range of animals that it appears very probable that if human beings were subjected to the same relative conditions a more or less severe form of a similar thyroid disturbance would result. A profound influence of pregnancy upon the maternal thyroid, which may develop into a pathologic condition, has to some extent been recognized, but the attention has been confined mainly to the maternal organism. The manifestations of the thyroid disturbance among domestic animals show very clearly, however, that the effects are more disastrous to the fetus than to the maternal organism. It is our opinion that when this subject has been thoroughly explored many of the cases of infantile fatality and of arrested development of children which are now vaguely designated as congen...