3,3'-Diiodothyronine sulfate cross-reactive material (compound W) in human newborns.

BACKGROUND: Thyrosulfoconjugation appears to facilitate fetal-to-maternal transfer of 3,3'-diiodothyronine-sulfate (T(2)S). Elevated maternal levels of T(2)S cross-reactive material (compound W) are found in humans, with higher levels found in venous cord blood than in arterial samples. These findings are consistent with the postulate that the placenta plays an essential role in compound W production. METHODS: Serum compound W levels were measured by a T(2)S-specific radioimmunoassay in 60 serum samples from newborns with hyperbilirubinemia, age 1-30 d. In addition, 59 maternal serum samples, from day 1 to day 7 after uneventful deliveries, were studied. RESULTS: As compared with day 1, at day 5, the mean (±SE) compound W level fell to 43.5 ± 6.8% (decay half-life (t(1/2)) = 4.12 d) and to 33.7 ± 4.6% (decay t(1/2) = 2.82 d) in the newborn and maternal groups, respectively. In the mothers, the level continued to decline along the same slope through day 7. In the newborns, however, the mean compound W level entered a slower phase of decay after the fifth day with a decay t(1/2) = 10.9 d. CONCLUSION: Compound W is cleared at similar rates in newborn and postpartum maternal sera. This is consistent with the postulate that compound W is produced in the placenta.

Phase 1 trial of 4 thyroid hormone regimens for transient hypothyroxinemia in neonates of <28 weeks' gestation.

BACKGROUND: Transiently low levels of thyroid hormones occur in approximately 50% of neonates born 24-28 weeks' gestation and are associated with higher rates of cerebral palsy and cognitive impairment. Raising hormone levels shows promise for improving neurodevelopmental outcome. OBJECTIVE: To identify whether any of 4 thyroid hormone supplementation regimens could raise T(4) and FT(4) without suppressing TSH (biochemical euthyroidism). METHODS: Eligible subjects had gestational ages between 24 07 and 2767 weeks and were randomized <24 hours of birth to one of six study arms (n = 20-27 per arm): placebo (vehicle: 5% dextrose), potassium iodide (30 microg/kg/d) and continuous or bolus daily infusions of either 4 or 8 microg/kg/d of T(4) for 42 days. T(4) was accompanied by 1 microg/kg/d T(3) during the first 14 postnatal days and infused with 1 mg/mL albumin to prevent adherence to plastic tubing. RESULTS: FT(4) was elevated in the first 7 days in all hormone-treated subjects; however, only the continuous 8 microg/kg/d treatment arm showed a significant elevation in all treatment epochs (P < .002 versus all other groups). TT(4) remained elevated in the first 7 days in all hormone-treated subjects (P < .05 versus placebo or iodine arms). After 14 days, both 8 microg/kg/d arms as well as the continuous 4 microg/kg/d arm produced a sustained elevation of the mean and median TT(4), >7 microg/dL (90 nM/L; P < .002 versus placebo). The least suppression of THS was achieved in the 4 microg/kg/d T(4) continuous infusion arm. Although not pre-hypothesized, the duration of mechanical ventilation was significantly lower in the continuous 4 microg/kg/d T(4) arm and in the 8 microg/kg/d T(4) bolus arm (P < .05 versus remaining arms). ROP was significantly lower in the combined 4 thyroid hormone treatment arms than in the combined placebo and iodine arms (P < .04). NEC was higher in the combined 8 microg/kg/d arms (P < .05 versus other arms). CONCLUSIONS: Elevation of TT(4) with only modest suppression of TSH was associated with trends suggesting clinical benefits using a continuous supplement of low-dose thyroid hormone (4 microg/kg/d) for 42 days. Future trials will be needed to assess the long-term neurodevelopmental effects of such supplementation.

Thyroid system immaturities in very low birth weight premature infants.

Continuing advances in the care of premature infants has contributed to the increased survival of very low birth weight premature infants. These infants are characterized by a variety of organ and physiological systems immaturities predisposing to deficiencies of postnatal adaptation and a high prevalence of neonatal morbidities. These morbidities have a major impact on postnatal mental and neurological outcomes. Thyroid hormones play a critical role in central nervous system development and function, and thyroid system immaturities as well as morbidity-related thyroid dysfunction (the nonthyroidal illness syndrome) contribute to the transient hypothyroxinemia of premature infants (THOP). Several studies have demonstrated a correlation of THOP with subsequent low IQ and neurologic sequelae in very low birth weight premature infants, and there is suggestive evidence that thyroid hormone supplementation in very low birth weight infants can improve mental outcome. Here, we review normal fetal thyroid system development and the system immaturities contributing to THOP and predisposing to nonthyroidal illness in very low birth weight infants.

3'-monoiodothyronine sulfate and Triac sulfate are thyroid hormone metabolites in developing sheep.

We used novel 3'-monoiodothyronine sulfate (3'-T1S) and 3,3',5-triiodothyroacetic acid sulfate (TriacS) RIAs to characterize sulfation pathways in fetal thyroid hormone metabolism. 3'-T1S and TriacS levels were measured in serum samples obtained from fetal (n = 21, 94-145 d gestational age), newborn (NB, n = 5), and adult sheep (AD, n = 5) as well as from fetuses after total thyroidectomy (Tx), or sham-operated twin fetuses controls, conducted at gestational age 110-113 d (n = 5). Peak levels (expressed as ng/dL) of both 3'-T1S and TriacS occurred at 130 d gestation. These levels in fetuses were higher than those in NB and AD. In Tx fetuses, there was a significant decrease in the mean serum level of 3'-T1S, but not TriacS. The decrease in 3'-T1S in Tx is similar to that observed for thyroxine sulfate (T4S) and 3,3',5'-triiodothyronine sulfate (rT3S), whereas TriacS levels were not altered in the hypothyroid state, similarly to 3,3',5-triiodothyronine sulfate (T3S). These data demonstrate that 3'-T1S and TriacS are normal thyroid hormone metabolites in ovine serum and that TriacS is likely derived from T3S or from the same precursor(s) as T3S.

Thyroid function and dysfunction in premature infants.

During the past four decades major advances in the management of premature infants have led to progressive reduction in mortality. During this period mortality in very low birth weight infants (VLBW, <1500 grams and <30 weeks gestation age) has decreased, and more than 50% of infants less than 24 weeks gestation age now survive, increasing the population of VLBW infants in intensive care nursery environments. Thyroid function in these infants is characterized by decreased TSH and T4 responses to parturition, low serum total T4 and TSH levels and variable free T4 concentrations during the first 2-4 postnatal weeks of life. These features reflect a state of transient hypothalamic-pituitary or central hypothyroidism. There is a high prevalence of morbidity in these infants, as well, often associated with further reductions in serum total T4, T3, TBG and TSH concentrations and variable levels of free T4 and reverse T3, resembling the non-thyroidal illness (NTI) syndrome in adults. The etiologic roles of thyroid system immaturity and NTI in the transient hypothyroxinemia of prematurity (THOP) and the impact of THOP on the subsequent neurological deficits in VLBW infants remains unclear. Several thyroxine supplementation trials have been conducted with inconclusive results. Further studies are planned or in progress.

Compound W, a 3,3'-diiodothyronine sulfate cross-reactive substance in serum from pregnant women--a potential marker for fetal thyroid function.

Compound W, a 3,3'-diiodothyronine sulfate (T2S) cross-reactive material in maternal serum, was found to be useful as a marker for fetal hypothyroidism. In the present report, we explored its biochemical properties and studied its concentrations in cord and in maternal serum obtained from various gestational periods and at term from different continents. Mean W concentrations, expressed as nmol/L T2S-equivalent, in maternal serum during gestation showed a moderate increase at 20-26 wk (1.57 nmol/L) and an accelerated increase to 34-40 wk (3.59 nmol/L). The mean serum level was relatively low in nonpregnant women (0.17 nmol/L). Compound W levels in cord and maternal serum at term were not significantly different among samples obtained from Taiwan compared with samples from the United States. The mean cord serum "corrected" (by hot acid digestion) concentrations of W were significantly higher than maternal serum concentrations at birth and were also higher in venous than in paired arterial samples, suggesting that the placenta may play a role in its production. We compared a total of 45 iodothyronine analogs by antibody, gel filtration, and HPLC chromatographic studies and found only one compound, N,N-dimethyl-T2S, that has close similarities to Compound W. Further studies are needed.

Fetal-to-maternal transfer of thyroid hormone metabolites in late gestation in sheep.

3,3'-Diiodothyronine sulfate (T2S) derived from T3 of fetal origin is transferred to the maternal circulation and contributes significantly to the maternal urinary pool. The present study quantitatively assesses the fetal to maternal transfer of T4 metabolites compared with those of T3. Labeled T4 or T3 was infused intravenously to four singleton fetuses in utero in each group at gestational age 138 +/- 3 d. Maternal and fetal serum and maternal urine samples were collected hourly for 4 h and at 24 h (serum) or in pooled 4-24 h samples (urine). Radioactive metabolites were identified by HPLC and by specific antibody in serum and urine extracts and expressed as percentage infusion dose per liter. The results demonstrate a rapid clearance of labeled T3 from fetal serum (disappearance T(1/2) of 0.7 h versus 2.4 h for T4 in the first 4 h). The metabolites found in fetal serum after labeled T3 infusion were T2S > T3 > T3S; in maternal urine, T2S > unconjugated iodothyronines (UI) > T3S > unknown metabolite (UM). After labeled T4 infusion, the metabolites in fetal serum were rT3 > T3 > T2S > T4S in the first 4 h, and rT3 = T3 = T4S = T2S > T3S at 24 h; in maternal urine we found T2S > UM > UI > T4S > T3S in the first 4 h and UM > T2S > UI in 4-24 h pooled sample. In conclusion, the conversion of T3 to T2S followed by fetal to maternal transfer of T2S and other iodothyronines appears to contribute importantly to maintaining low fetal T3 levels in late gestation.

A short history of pediatric endocrinology in North America.

Pediatric endocrinology evolved as a subspecialty from the era of biochemical and metabolic clinical investigation led by John Howland, Edwards Park, and James Gamble at Johns Hopkins; Allan Butler at Boston University and Harvard University; Daniel Darrow at Yale University; and Irving McQuarrie at the University of Rochester and the University of Minnesota during the early 20th century. The father of the new subspecialty was Lawson Wilkins, a private pediatric practitioner in Baltimore, Maryland, who was invited by Dr. Edwards Park to establish an endocrine clinic at the Harriet Lane Home at Johns Hopkins in 1935. Dr. Wilkins managed his practice and the clinic until 1946, when, at the age of 52, he accepted a full-time position at the University. Dr. Nathan Talbot was invited to develop a pediatric endocrine clinic at Massachusetts General Hospital by Allan Butler in 1942. These units and their associated subspecialty training programs during the 1950s and 1960s provided the large majority of the second-generation pediatric endocrinologists who went on to establish endocrine subspecialty programs in university medical centers in North America as well as Europe and South America. Diabetes as a clinical pediatric discipline evolved in parallel from the early clinics of Elliott Joslin and Priscilla White in Boston, M.C. Hardin and Robert Jackson at the University of Iowa, George Guest at the University of Cincinnati Children's Hospital, and Alex Hartman at the St. Louis Children's Hospital. The Lawson Wilkins Pediatric Endocrine Society was founded in 1971, and the Council on Diabetes and Youth was established within the American Diabetes Association in 1980. Medical and economic factors led to increasing integration of pediatric diabetes and general endocrine care and training, and diabetes care now is a major activity within the subspecialty of pediatric endocrinology. The growth of pediatric endocrinology in North America has paralleled the growth of academic medicine during the past half-century. In 2002, there were 72 training programs in North America: 65 in the United States and seven in Canada. The endocrinology sub-board of the American Board of Pediatrics was established in 1978 to certify training and competence in endocrinology, including diabetes. By 2002, the board had certified 927 pediatric endocrinologists. Pediatric endocrine subspecialists during the past half-century have contributed major advances in our understanding of the ontogeny of endocrine systems and the diagnosis and treatment of fetal-perinatal endocrine disorders; newborn screening for endocrine and metabolic disorders; the physiology and therapies for disorders of sexual differentiation and pubertal maturation; the development of anthropometric standards for childhood growth and development; the characterization and physiology of hormone systems, including receptors and hormone actions; the molecular genetics of a number of congenital endocrine disorders and heritable endocrine diseases; development of pediatric endocrine diagnostics and reference standards; the pathophysiology and management of autoimmune endocrine disease; and development of a growing armamentarium of therapeutic agents for treatment of endocrine and metabolic diseases.

The diagnosis of congenital adrenal hyperplasia in the newborn by gas chromatography/mass spectrometry analysis of random urine specimens.

Definitive neonatal diagnosis of congenital adrenal hyperplasia (CAH) is frequently complicated by normal 17-hydroxyprogesterone levels in 21-hydroxylase-deficient patients, residual maternal steroids, and other interfering substances in neonatal blood. In an effort to improve the diagnosis, we developed a gas chromatography/mass spectrometry method for simultaneous measurement of 15 urinary steroid metabolites as early as the first day of life. Furthermore, we developed 11 precursor/product ratios that diagnose and clearly differentiate the four enzymatic deficiencies that cause CAH. Random urine samples from 31 neonatal 21-hydroxylase-deficient patients and 59 age-matched normal newborns were used in the development. Additionally, samples from two 11 beta-hydroxylase-deficient patients and one patient each for 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase deficiencies were used. The throughput for one bench-top gas chromatography/mass spectrometry instrument is 20 samples per day. Thus, this method affords an accurate, rapid, noninvasive means for the differential diagnosis of CAH in the newborn period without the need for invasive testing and ACTH stimulation.