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Biomedical subjects

P de Nayer

Publications and source records attributed to P de Nayer.

At least 19 recordsLinked to original sources
PubMed1992

Maternal and neonatal thyroid function at birth in an area of marginally low iodine intake.

Thyroid function was evaluated in cord serum of healthy full-term newborns and compared to that of mothers immediately after parturition. The study was carried out in an area without overt iodine deficiency, but with a marginal iodine supply (less than 100 micrograms/day in 80% of women). The aim of the study was to delineate the interrelationships between the thyroid statuses of mother and child at birth. Maternal thyroid function was characterized at delivery by relative hypothyroxinemia; increased T3/T4 ratios, indicating preferential T3 secretion; slightly increased TSH levels within the normal range in 97% of women; increased serum thyroglobulin (TG) values, which were above normal in 60% of women; and also goiter formation in almost 10% of women. The findings indicated glandular stimulation and confirmed our earlier reports that pregnancy constitutes a stress for the maternal thyroid economy, enhanced by the limited availability of iodine in the diet. By contrast, newborns showed a strikingly distinct pattern: there was no relative hypothyroxinemia and free T4 levels were significantly higher than in the respective mothers (19.4 vs. 14.7 pmol/L; P less than 0.001). In spite of these differences, however, mean neonatal TSH and TG levels were significantly higher than maternal values, respectively 6.0 vs. 1.9 mU/L for TSH (P less than 0.001) and 70 vs. 40 micrograms/L for TG (P less than 0.001). Furthermore, neonatal TG and TSH levels increased in parallel and were highly correlated with maternal data, suggesting a regulatory link between both thyroid economies. The results suggested that the common regulatory link is the limited availability of the iodine supply. In conclusion, the present study demonstrates that even in conditions with a marginally low iodine intake, pregnancy constitutes a stimulus for both the maternal and newborn thyroids. Changes in both groups are associated and the abnormalities in TSH and TG are amplified in the newborns. The TSH and TG alterations at birth in full-term healthy newborns, associated with similar alterations in maternal thyroid function, provide evidence for a common stimulatory factor, relative iodine deficiency. The data emphasize the hypersensitivity of neonatal thyroid function to marginal iodine deficiency and point to the need to increase the iodine supply in groups at risk, such as women during pregnancy, and also newborns in the perinatal period.

Cohort Studies↗
PubMed1991

Pregnancy in patients with mild thyroid abnormalities: maternal and neonatal repercussions.

A prospective study was undertaken during pregnancy in 120 euthyroid women presenting with mild thyroid abnormalities (TA): 11 with a past history of thyroid disorder, 44 with goiter, 20 with nodules, and 45 with thyroid autoantibodies. The aims of the study were to assess whether the pattern of thyroid alterations during gestation was different in women with TA compared to that in healthy control pregnant subjects and to evaluate possible obstetrical and neonatal repercussions. The overall prevalence of underlying subtle thyroid abnormalities in the cohort was 17%, probably as the result of the environmental moderately low iodine intake. Despite the intrinsic heterogeneity of the four groups of women with TA, the adaptation of the thyroid to the stress of pregnancy was different from that of the control subjects. Noteworthy were 1) the marked elevation of serum thyroglobulin in women with past history of thyroid disorder, goiter and thyroid nodules; 2) the increase in goiter size in a third of the goitrous women, associated with biochemical evidence of functional stimulation of the gland; 3) the indirect evidence of partial thyroidal autonomy in goitrous patients; and 4) the increase in the number and size of thyroid nodules during gestation. Taken together, the data indicated that pregnancy was associated with a greater thyroidal risk in patients with TA compared to healthy subjects. In relation to thyroid autoimmunity, most patients remained euthyroid during gestation, but in a few cases, TSH was elevated at delivery, suggesting diminished thyroidal reserve. Also, 40% of newborns from mothers with thyroid autoimmunity had elevated thyroid peroxidase antibody titers at birth, and there was a highly significant correlation between maternal and neonatal thyroid peroxidase antibody titers. Finally, thyroid autoimmunity was clearly associated with an increased risk of spontaneous abortion (13.3 vs. 3.3%; P less than 0.001). Thyroid function in newborns from mothers with TA was normal and not different from that in controls; similarly, obstetrical features were similar in patients with TA and control subjects. In conclusion, pregnancy is associated with a greater thyroidal risk in women with TA, thereby emphasizing a potential link between pregnancy and thyroid disorders. It is recommended that patients with known, even subtle, thyroid abnormalities be closely monitored during pregnancy, in particular those with a goiter, nodules, or thyroid autoimmunity, especially in areas with a moderately low iodine intake, where the prevalence of mild thyroid disturbances is high.

Adult↗
PubMed1990

Metabolic and cardiovascular responses to exogenous triiodothyronine favour nontreatment of a girl with familial receptor-positive thyroid hormone resistance.

A father and daughter with inappropriate TSH secretion due to generalized relative receptor-positive thyroid hormone resistance are described. Minor variations of tissue peripheral resistance were observed in the adolescent girl. Shortened ankle reflex relaxation time and other clinical signs were consistent with a mild hyperthyroid state of the neuromuscular unit. The response of sex hormone-binding globulin concentration, 24 hour-ECG data and left ventricular echocardiographic parameters to increasing doses of triiodothyronine confirmed an euthyroid state of heart and liver tissue in the presence of excess thyroid hormone. Based on these findings and the benign course of the disease, treatment was withheld. Careful assessment, including echocardiography and 24 hour-ECG, of the functional state of thyroid hormone target tissues during triiodothyronine administration is recommended in these patients. No treatment is required when the functional state of the target tissues is eumetabolic.

Adolescent↗
PubMed1990

Regulation of maternal thyroid during pregnancy.

A prospective study was undertaken in 606 healthy women during pregnancy to evaluate the changes occurring in maternal thyroid economy as a result of 1) the increased thyroid hormone-binding capacity of serum, 2) the effects of increased levels of hCG on TSH and on the thyroid, and 3) a marginally low iodine intake in the population (50-75 micrograms/day). Four main features were observed. First, thyroidal activity adjusted to the marked increase in serum T4-binding globulin: pregnancy was accompanied by an overall reduction in the T4/T4-binding globulin ratio, with lower free T4 and T3 levels, although in most cases free hormone levels remained within the normal range. The adjustment of thyroidal output of T4 and T3 did not occur similarly in all subjects. In approximately one third of the women, there was relative hypothyroxinemia, higher T3/T4 ratios (presumably indicating preferential T3 secretion), and higher, although normal, serum TSH concentrations. Second, high hCG levels were associated with thyroid stimulation, both functionally (lower serum TSH) and anatomically (increased thyroid size). The data are consistent with a TSH-like effect of hCG on the thyroid. Hence, regulation of the maternal thyroid is complex, resulting from both elevated hCG (mainly in the first half of gestation) and increasing TSH (mainly in the second half of gestation). Third, a significant increase in serum thyroglobulin levels was observed throughout gestation, especially during the last trimester. Fourth, increased thyroid volume was common, and goiter formation not uncommon (goiter was found in 9% of women at delivery). In conclusion, the alterations in maternal thyroid function during gestation are intricate and far from fully understood. In areas of marginally low iodine intake, gestation is associated in a significant number of women with relative hypothyroxinemia, increased thyroglobulin, and enlarged thyroid.

Chorionic Gonadotropin↗
PubMed1988

Massive bone allografts in large skeletal defects after tumor surgery: a clinical and microradiographic evaluation.

Massive deep-frozen bone allografts were implanted in 13 patients after en bloc tumor resection. Patients were followed up for 14 months to 17 years. Most of the reconstructive procedures included a segmental bone allograft with knee or ankle fusion. Graft infections were the most critical complications in regard to the end results, finally requiring amputation in two cases. There were three stress fractures; two of which were successfully treated without further complication. Graft incorporation was assessed by bone scintimetry in four cases. Isotope uptake by the center of the graft was found to be superior to control bone segments at only 15 years after surgery. Two recovered allograft specimens were available for a microradiographic study. Creeping substitution was a very slow process, initiated at the outer surface of the graft and characterized at 2-3 years after implantation by large, incompletely filled osteons. The present investigation demonstrates that massive bone allografts are very slowly revascularized and are intimately anchored by the host bone. Provided that tumor control is effective and graft infection is avoided, reconstructive surgery with massive bone allografts represents a successful alternative to prosthetic implants in young adult with a long life expectancy.

Adolescent↗
PubMed1986

Sex hormone-binding protein in hyperthyroxinemic patients: a discriminator for thyroid status in thyroid hormone resistance and familial dysalbuminemic hyperthyroxinemia.

Sex hormone-binding globulin (SHBG) levels in serum are affected by thyroid status; hyperthyroidism is associated with high SHBG levels, whereas hypothyroid patients have low or normal SHBG levels. This study was undertaken to test the usefulness of SHBG determinations to define the thyroid status in two hyperthyroxinemic states: thyroid hormone resistance (THR) and familial dysalbuminemic hyperthyroxinemia (FDH). Serum SHBG levels were determined in 193 patients and 26 normal subjects using an IRMA-type RIA. In the control group, the mean values in women (58.9 nmol/liter) and men (32.7 nmol/liter) were significantly different (P less than 0.001). In adult subjects with THR, SHBG levels were within the normal range, with mean values of 54.8 nmol/liter (range, 28.7-82.5 nmol/liter) in women and 18 and 20 nmol/liter in two men. In FDH subjects, the mean SHBG levels did not differ from the normal values; they averaged 60.7 nmol/liter in women and 42.3 nmol/liter in men. From these data we conclude that in THR and FDH, free T4 levels elicit an appropriate hepatic response corresponding to the euthyroid status of these subjects. SHBG determination may, therefore, serve as an in vitro test for end-organ sensitivity to thyroid hormones.

Drug Resistance↗