triiodothyronine--reverse and Infant--Newborn--Diseases

Topics: Animals; Feedback; Homeostasis; Humans; Hypothalamo-Hypophyseal System; Hypothyroidism; Infant, Newborn; Infant, Newborn, Diseases; Infant, Premature; Rats; Receptors, Cell Surface; Receptors, Thyroid Hormone; Sheep; Thyroid Diseases; Thyroid Gland; Thyrotropin; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse

Topics: Canada; Congenital Hypothyroidism; Fetal Blood; Humans; Hypothyroidism; Infant, Newborn; Infant, Newborn, Diseases; Mass Screening; Radioimmunoassay; Thyroid Function Tests; Thyrotropin; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse; United States

Assessment of thyroid function in preterm neonates (PTN) 27-29 weeks of gestational age.. 80 PTN, gestational age 27 weeks in 24, 28 weeks in 28, and 29 weeks in 28. Neonates were classified as healthy (n=17) or sick (n=63). Measurement of serum TSH, free T4, T4, T3 and rT3 in the mother and in the cord at the time of delivery, and in the infant at 1 hour, 24 hours, 1 week, 3 weeks, and 2 and 4 months of postnatal age.. In healthy and sick preterms, TSH values peaked at 1 hour and decreased thereafter. Healthy PTN presented a peak in free T4 values at 24 hours that was not observed in sick neonates. Sick PTN had a lower TSH peak and lower free T4 values at 24 hours and 1 week than healthy ones (p < 0.05). Healthy PTN 27-29 weeks had lower TSH peak at 1 hour and lower free T4, T3 and T4 values during the first 2 months than healthy PTN 30-35 weeks (PTN30-35w) previously evaluated (p < 0.05). However, at all postnatal times healthy preterms had free T4 values above -2 SD of the mean values of healthy PTN30-35w. A wide range of free T4 values was observed in the sick group. Free T4 values above -2 SD of the mean values of healthy PTN30-35w were detected in a high proportion of sick PTN (58.3% at 24 hours, 73.5% at 1 week, 93.9% at 3 weeks, 85.1% at 2 months and 100% at 4 months).. Prematurity and disease influence thyroid function, and consequently thyroid function should be individually assessed in preterms 27-29 weeks of gestation during the first 2 months of life.

Topics: Birth Weight; Databases, Factual; Gestational Age; Humans; Infant, Newborn; Infant, Newborn, Diseases; Infant, Premature; Longitudinal Studies; Neonatal Screening; Prospective Studies; Spain; Thyroid Function Tests; Thyroid Gland; Thyrotropin; Thyroxine; Time Factors; Triiodothyronine; Triiodothyronine, Reverse

Topics: Asphyxia Neonatorum; Humans; Hypoglycemia; Infant, Newborn; Infant, Newborn, Diseases; Infections; Meconium; Pneumonia, Aspiration; Surgical Procedures, Operative; Thyroid Gland; Thyroid Hormones; Thyrotropin; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse

Topics: Female; Fetus; Graves Disease; Humans; Hyperthyroidism; Hypothyroidism; Immunoglobulin G; Immunoglobulins, Thyroid-Stimulating; Infant, Newborn; Infant, Newborn, Diseases; Pregnancy; Pregnancy Complications; Propylthiouracil; Thyrotropin; Triiodothyronine; Triiodothyronine, Reverse

Topics: Adult; Age Factors; Female; Fetal Blood; Humans; Hyperthyroidism; Hypothyroidism; Infant, Newborn; Infant, Newborn, Diseases; Male; Pregnancy; Thyroid Hormones; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

A new sensitive radioimmunoassay method for measuring reverse triiodothyronine (rT3) concentrations in dried blood samples, designed to screen newborn infants for congenital hypothyroidism, has been developed. Paper strips are impregnated with cord blood and dried. Duplicate 5-mm diameter discs are punched from the paper strips and added directly to the radioimmunoassay reaction mixture. After incubation, bound and free hormone are separated by dextran-coated charcoal. The disc remains in the solution throughout the procedure and the assay can be completed within 24 hr. Recovery of rT3 is greater than 95% and coefficients of variation are 9.4% (intraassay) and 12.2% (interassay) at an rT3 concentration of 220 ng/dl. At very low rT3 concentrations (25 ng/dl), coefficients of variation are 14.2% (intraassay) and 18.7% (interassay). The method readily detects 12.5 ng/dl of rT3. With this paper disc method, rT3 was measured in 38 newborns and compared with serum rT3 measured in the same subjects by a standard radioimmunoassay method. The correlation between rT3 values measured in dried blood disc and in serum was very high (r = 0.918). The rT3 in dried blood discs from the cord blood of 745 normal newborns was 228.9 +/- 76.0 ng/dl (mean +/- SD). In contrast, two infants with proven congenital hypothyroidism had rT3 values of 35 and 75 ng/dl, respectively. This study indicates that rT3 can be easily measured in dried blood discs and suggests that the described method may be a useful screening procedure in a program for the detection of neonatal hypothyroidism.

Topics: Congenital Hypothyroidism; Fetal Blood; Humans; Hypothyroidism; Infant, Newborn; Infant, Newborn, Diseases; Paper; Radioimmunoassay; Statistics as Topic; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse