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Corticosteroids and thyroid function. Different effects on plasma volume, thyroid hormones and thyroid hormone-binding proteins after oral and intravenous administration.

The influence of glucocorticosteroids on plasma volume, thyroid hormones and thyroid hormone-binding proteins was studied in 17 patients. Plasma volume was not affected either by i.v. beta-methasone (6 mg daily) or by oral prednisolone (45--180 mg daily) given for 5 days. The serum T3 concentration decreased while rT3 increased independently of the route of administration of corticosteroids. Serum T4 concentration decreased after i.v. but not after oral administration of corticosteroids. Oral steroids as compared to i.v. increased the 125I-triiodothyronine uptake test value. The serum TBG concentration decreased independently of the route of administration, while the serum TBPA concentration increased after oral corticosteroids but was unchanged after i.v. treatment. The serum TSH concentration was slightly reduced. About half of the patients were given both corticosteroids and nutrition i.v. and the other half were given all treatment by mouth. The part played by the route of administration of corticosteroids and calories, respectively, cannot be evaluated at present but these factors seem to be of importance.

Administration, Oral↗

A water-soluble fragment of the thyroid-stimulating hormone receptor which binds both thyroid-stimulating hormone and thyroid-stimulating hormone receptor antibodies.

Previous studies have shown that freezing and thawing of human thyroid homogenates releases a water-soluble substance which reversibly binds to TSH-receptor antibodies. This substance has been designated long-acting thyroid stimulator absorbing activity (LAA). We now describe a new method for measuring LAA based on the TSH-receptor assay and application of the technique to the study of LAA. Our results indicate that LAA is a heat-labile glycoprotein which co-elutes with haemoglobin on gel filtration. Furthermore, LAA is retarded by columns of Sepharose-TSH but not by Sepharose coupled to human chorionic gonadotrophin, normal immunoglobulin G or bovine serum albumin, suggesting that LAA contains a binding site for TSH as well as for TSH-receptor antibodies. It would seem therefore that LAA is a water-soluble fragment of the TSH receptor possibly resulting from proteolytic cleavage of the receptor at a site close to the cell surface.

Antibodies↗

Cyclic AMP-stimulated fluid transport in the thyroid: influence of thyroid stimulators, amiloride and acetazolamide on the dynamics of domes in monolayer cultures of porcine thyroid cells.

Confluent monolayer cultures of porcine thyroid cells form dome-shaped elevations by local separation from the plastic culture dish. Formation of domes by epithelial cells in culture is generally considered to be evidence of fluid transport. A computer-controlled data acquisition system was developed to quantitate fluid transport in thyroid cultures by serial measurements of dome elevation. Thyrotrophin (10 mU/ml), prostaglandin E2 (PGE2; 0.01-1 mumol/l), forskolin (1 mumol/l), 8-(4-chlorophenylthio)adenosine 3':5'-cyclic monophosphate (0.5 mmol/l) and 3-isobutyl-1-methyl-xanthine (0.5 mmol/l) promoted increases in dome height over 5-120 min. Dome growth in the presence of PGE2 (1 mumol/l) was inhibited by amiloride (0.1-100 mumol/l), ouabain (200 mumol/l), or by removal of bicarbonate and glucose from the medium. In media of reduced bicarbonate concentration (1 mmol/l compared with the control concentration of 10 mmol/l), dome growth was inhibited by acetazolamide (0.01-1 mmol/l). These data are consistent with cyclic AMP-stimulated transport of fluid from apical to basal pole of the cells, dependent on sodium entry through the apical pole by an Na+/H+ exchanger.

Acetazolamide↗

[Studies on cytosol thyroid hormone binding proteins in the rat liver: Part II. Alterations of thyroid hormone binding proteins in various thyroid function states].

Alterations of binding characteristics of cytosolic thyroid hormone binding proteins (CTHBPs) were examined in livers of rats with different thyroid function. Seven days after thyroidectomy, rats were divided into three groups. Group I received no treatment. Group II was treated with 230 ng triiodothyronine (T3)/100 g body weight per day for three days, and Group III with 40 micrograms T3/100 g body weight per day for three days. On the fourth day, each rat was given 0.7 microCi of 125I-T3/100 g body weight intraperitoneally and exsanguinated two hours later. During three days' treatment, body weight in Group II increased significantly compared with that in Group I (P less than 0.05), and body weight in Group III actually decreased. The ratio of liver weight to body weight in Group II was significantly higher than that in Group I or Group III (P less than 0.01). Percent distributions of 125I-T3 in cytosol fraction per liver or concentrations of cytosolic protein did not differ significantly among these three groups. Serum T3 concentrations (mean +/- SD ng/ml: Group I; not detectable, Group II; 0.50 +/- 0.27, Group III; 7.10 +/- 2.31), cytosolic T3 concentrations (mean +/- SD ng/ml: Group I; not detectable, Group II; 0.59 +/- 0.26, Group III; 10.38 +/- 3.08) and mitochondrial alpha-glycerophosphate dehydrogenase activities (mean +/- SD delta OD500 millimicrons/min/mg: Group I; 28.0 +/- 1.5, Group II; 46.7 +/- 7.3, Group III; 267.7 +/- 9.1) suggested that Group I was in hypothyroid state, Group II in euthyroid state and Group III in thyrotoxic state. Binding characteristics of cytosolic T3 binding protein (CT3BP) were different among the three groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Detection of thyroid toxicants in a tier I screening battery and alterations in thyroid endpoints over 28 days of exposure.

Phenobarbital (PB), a thyroid hormone excretion enhancer, and propylthiouracil (PTU), a thyroid hormone-synthesis inhibitor, have been examined in a Tier I screening battery for detecting endocrine-active compounds (EACs). The Tier I battery incorporates two short-term in vivo tests (5-day ovariectomized female battery and 15-day intact male battery using Sprague-Dawley rats) and an in vitro yeast transactivation system (YTS). In addition to the Tier I battery, thyroid endpoints (serum hormone concentrations, liver and thyroid weights, thyroid histology, and UDP-glucuronyltransferase [UDP-GT] and 5'-deiodinase activities) have been evaluated in a 15-day dietary restriction experiment. The purpose was to assess possible confounding of results due to treatment-related decreases in body weight. Finally, several thyroid-related endpoints (serum hormone concentrations, hepatic UDP-GT activity, thyroid weights, thyroid follicular cell proliferation, and histopathology of the thyroid gland) have been evaluated for their utility in detecting thyroid-modulating effects after 1, 2, or 4 weeks of treatment with PB or PTU. In the female battery, changes in thyroid endpoints following PB administration, were limited to decreased serum tri-iodothyronine (T3) and thyroxine (T4) concentrations. There were no changes in thyroid stimulating hormone (TSH) concentrations or in thyroid gland histology. In the male battery, PB administration increased serum TSH and decreased T3 and T4 concentrations. The most sensitive indicator of PB-induced thyroid effects in the male battery was thyroid histology (pale staining and/or depleted colloid). In the female battery, PTU administration produced increases in TSH concentrations, decreases in T3 and T4 concentrations, and microscopic changes (hypertrophy/hyperplasia, colloid depletion) in the thyroid gland. In the male battery, PTU administration caused thyroid gland hypertrophy/hyperplasia and colloid depletion, and the expected thyroid hormonal alterations (increased TSH, and decreased serum T3 and T4 concentrations). The dietary restriction study demonstrated that possible confounding of the data can occur with the thyroid endpoints when body weight decrements are 15% or greater. In the thyroid time course experiment, PB produced increased UDP-GT activity (at all time points), increased serum TSH (4-week time point), decreased serum T3 (1-and 2-week time points) and T4 (all time points), increased relative thyroid weight (2- and 4-week time points), and increased thyroid follicular cell proliferation (1- and 2-week time points). Histological effects in PB-treated rats were limited to mild colloid depletion at the 2- and 4-week time points. At all three time points, PTU increased relative thyroid weight, increased serum TSH, decreased serum T3 and T4, increased thyroid follicular cell proliferation, and produced thyroid gland hyperplasia/hypertrophy. Thyroid gland histopathology, coupled with decreased serum T4 concentrations, has been proposed as the most useful criteria for identifying thyroid toxicants. These data suggest that thyroid gland weight, coupled with thyroid hormone analyses and thyroid histology, are the most reliable endpoints for identifying thyroid gland toxicants in a short-duration screening battery. The data further suggest that 2 weeks is the optimal time point for identifying thyroid toxicants based on the 9 endpoints examined. Hence, the 2-week male battery currently being validated as part of this report should be an effective screen for detecting both potent and weak thyroid toxicants.

Animals↗

Thyroid antibodies in spontaneous autoimmune thyroiditis in the Buffalo rat.

Thyroid antibodies in the sera of BUF rats are closely correlated with spontaneous thyroiditis; their detection may facilitate the study of this animal model of organ-specific autoimmunity. In a group of 115 retired BUF breeders (females older than 1 year), 26% had mononuclear cell infiltration of the thyroid and high titers of thyroid antibodies detectable by indirect immunofluorescence (IF) and chromic chloride passive hemagglutination (CCH). In contrast, low-titered thyroid antibodies were present in 9% of the rats that had normal thyroids. Sequential studies performed on a group of 76 neonatally thymectomized BUF rats showed that at 2 months 24% had high titers of thyroid antibodies detectable by IF and 8% by CCH and at 3 months these percentages increased to 27% by IF and 25% by CCH. When the rats were sacrificed at 4 months, at a time when spontaneous disease is not seen in untreated animals, 26% were found to have mononuclear cell infiltration of their thyroids. Approximately 75% of these rats with thyroiditis had been positive for thyroid antibodies at 2 months and 90% at 3 months. At sacrifice all of these animals had high-titered antibodies to thyroid antigens. In contrast, low-titered thyroid antibodies were present in 36% of the animals without thyroiditis. Intravenous injection of BUF thymus cells into neonatally thymectomized rats failed to reduce the incidence of thyroiditis and thyroid antibodies. Approximately 33% of these animals had both thyroid infiltration and serum antibodies, whereas 19% of those with normal thyroids had low-titered thyroid antibodies. Titers of circulating thyroid antibodies were closely correlated with the initial and intermediate stages of thyroiditis, i.e., animals with less infiltration had the lowest titers, whereas animals with intermediate levels of infiltration had high antibody titers. On the other hand, rats with a high degree of thyroid infiltration had relatively lower titers of thyroid antibodies. Direct IF of infiltrated thyroids revealed the presence of rat immunoglobulins in these organs, suggesting a possible direct or indirect role of autoantibodies in the pathogenesis of the disease. We attempted to detect delayed hypersensitivity by skin testing with thyroid antigens and observing reactions at 4, 24, and 48 hr. All of 123 rats were negative, 20% of which had thyroiditis and thyroid antibodies. No serum MIF activity was detected in rats with thyroiditis and those with normal thyroids. The absence of delayed hypersensitivity reactions in these experiments provides further support for the contention that spontaneous thyroiditis in the BUF rat may be antibody mediated.

Animals↗

HLA class II antigen expression and the autoimmune thyroid response in patients with benign and malignant thyroid tumors.

To further understand the relationship between the immune system and the neoplastic human thyroid cell we investigated the degree of intrathyroidal lymphocytic infiltration and thyroid HLA class II expression in 17 patients with thyroid tumors. In another 60 thyroid tumor patients the association of thyroidal lymphocytic infiltration with thyroid autoantibody production was analyzed. In total 117 thyroid tissues were examined including tissue obtained at autopsy (n = 28), fetal thyroid tissue (n = 4), thyroid samples obtained from areas distant from benign follicular adenomas (n = 5), and 80 abnormal thyroids including patients with benign (n = 53) or malignant (n = 24) thyroid tumors and Hashimoto's thyroiditis (n = 3). Normal adult and fetal thyroid tissue had no significant lymphocytic infiltration and no detectable HLA-DR, -DP, or -DQ antigens on their thyroid follicular epithelial cells. The degree of lymphocytic infiltration in the nonneoplastic thyroid tissue of thyroid glands with benign and malignant thyroid tumors varied considerably and correlated with the presence and titer of serum thyroid autoantibodies measured by sensitive ELISA techniques. However, all but one of the benign follicular adenomas had thyroid cells negative for HLA class II determinants despite the presence of infiltrating lymphocytes, while 7 of 10 thyroid carcinomas expressed class II antigen (principally HLA-DR) even when only minor degrees of lymphocytic infiltration were present. These data indicate a correlation between lymphocytic infiltrates and serum thyroid autoantibody titers but the relationship with HLA class II expression is more complex. Since we have previously shown that HLA class II antigen expression can be induced by local interferon-gamma secretion, presumably from activated T cells, we conclude that estimates of simple thyroid lymphocytic infiltration and serum autoantibody secretion do not correlate with the degree of intrathyroidal T-cell activation. Furthermore, our observation of increased expression of HLA class II antigens in thyroid cancer suggests considerable cellular heterogeneity in susceptibility to HLA class II antigen induction in human thyroid disease.

Adenoma↗

Recent developments in the investigation of thyroid regulation and thyroid carcinogenesis.

This review covers new mechanistic information spanning the past 10 years relevant to normal and abnormal thyroid growth and function that may assist in the risk assessment of chemicals inducing thyroid follicular cell neoplasia. Recent studies have shown that thyroid regulation occurs via a complex interactive network mediated through several different messenger systems. Increased thyroid-stimulating hormone (TSH) levels activate the signal transduction pathways to stimulate growth and differentiation of the follicular cell. The important role of TSH in growth as well as in function helps to explain how disruptions in the thyroid-pituitary axis may influence thyroid neoplasia in rodents. New investigations that couple mechanistic studies with information from animal cancer bioassays (e. g., sulfamethazine studies) confirm the linkage between prolonged disruption of the thyroid-pituitary axis and thyroid neoplasia. New initiation/promotion studies in rodents also support the concept that chronic stimulation of the thyroid induced by goitrogens can result in thyroid tumors. Some of these studies confirm previous suggestions regarding the importance of chemically induced thyroid peroxidase inhibition and the inhibition of 3,3',5, 5'-tetraiodothyronine (T4, thyroxine) deiodinases on disruption of the thyroid-pituitary axis leading to thyroid neoplasia. Some comparative physiologic and mechanistic data highlight certain differences between rodents and humans that could be expected to confer an increased vulnerability of rodents to chronic hypersecretion of TSH. New data from epidemiologic and molecular genetic studies in humans contribute further to an understanding of thyroid neoplasia. Acute exposure to ionizing radiation, especially in childhood, remains the only verified cause of thyroid carcinogenesis in humans. Iodine deficiency studies as a whole remain inconclusive, even though several new studies in humans examine the role of dietary iodine deficiency in thyroid cancer. Specific alterations in gene expression have been identified in human thyroid neoplasia, linked to tumor phenotype, and thus oncogene activation and tumor-suppressor gene inactivation may also be factors in the development and progression of thyroid cancer in humans. An analysis by the U.S. EPA Risk Assessment Forum, prepared as a draft report in 1988 and completed in 1997, focused on the use of a threshold for risk assessment of thyroid follicular tumors. New studies, involving several chemicals, provide further support that there will be no antithyroid activity until critical intracellular concentrations are reached. Thus, for chemically induced thyroid neoplasia linked to disruptions in the thyroid-pituitary axis, a practical threshold for thyroid cancer would be expected. More information on thyroid autoregulation, the role of oncogene mutations and growth factors, and studies directly linking persistently high TSH levels with the sequential cellular development of thyroid follicular cell neoplasia would provide further confirmation.

Adenocarcinoma, Follicular↗

Long-term outcome of interferon-alpha-induced thyroid autoimmunity and prognostic influence of thyroid autoantibody pattern at the end of treatment.

Thyroid autoimmunity and dysfunction have been widely reported as side effects of interferon-alpha (IFN-alpha) treatment, but the literature lacks data regarding the long-term course of these complications, clinical observation being limited to 6-12 months off therapy. Our study is the first that has aimed to evaluate the natural history of IFN-related thyroid autoimmunity during a 6.2-yr follow-up after the IFN-alpha withdrawal as well as to investigate the potential role of the autoantibody pattern at the end of treatment to predict the long-term outcome. Our study group included 114 patients (79 males, 35 females), mean age 48 yr (range 23-67 yr) with no preexisting thyroid disease, undergoing a 12-month treatment with recombinant IFN-alpha for C virus-related chronic active hepatitis. Thyroid autoimmunity (serum TgAb and TPOAb) and function (serum FT(4), FT(3), TSH) were retrospectively evaluated at the end of IFN therapy, 6 months after IFN withdrawal and after a median period of 6.2 yr (range 5.5-8.4 yr). At the end of treatment, 78 patients were negative for thyroid autoantibodies (Abs-) and all but one of them remained so for the following evaluations. The remaining 36 patients had thyroid autoantibodies (Abs+) at the end of treatment, and they subsequently showed a heterogeneous behavior: 16 patients remained Abs+ for the whole length of the study (persistent thyroiditis); 10 patients became Abs- 6 months off therapy but were again Abs+ 6.2 yr later (remitting/relapsing thyroiditis); 10 patients reverted to autoantibody negativity at different observation times (transient thyroiditis). The absence of thyroid autoantibodies at the end of treatment was a protective factor for the successive development of thyroiditis (odds ratio: 0.02, confidence interval (CI) 95%: 0-0.1). On the contrary, the positivity for TgAb and/or TPOAb at high titers at the end of IFN treatment was significantly related to the highest risk of having chronic thyroiditis (odds ratio: 17.3, CI 95%: 3.2-91.7 for TgAb levels > 50 degree percentile; odds ratio: 7.3, CI 95%: 1.5-35.2 for TPOAb levels > 50 degree percentile). None of the patients showed overt thyroid dysfunction throughout the study, whereas a subclinical hypothyroidism was found in 12 patients. In all 12 cases, the functional abnormality was accompanied by the presence of thyroid autoantibodies. Eight of these 12 patients belonged to the group with persistent thyroiditis (P < 0.05). The absence of thyroid autoantibodies at the end of treatment was a protective factor for the successive development of thyroid dysfunction (odds ratio: 0.06, CI 95%: 0.01-0.56). On the contrary, the positivity for both TgAb and TPOAb at the end of IFN therapy was significantly correlated with the highest risk of having subclinical hypothyroidism 6.2 yr. later (odds ratio: 38.7; CI 95%: 6.2-242). Our study demonstrates that in patients undergoing an IFN-alpha therapy for chronic hepatitis C and with no evidence of preexisting thyroid disease: 1) the negativity for thyroid autoantibodies after IFN treatment is a protective factor for the developing thyroid autoimmunity and/or dysfunction in following years; 2) the IFN-alpha-related thyroid autoimmunity is not a complete reversible phenomenon because some patients can develop chronic thyroiditis; 3) high autoantibody levels at the end of IFN therapy are related to the risk of having chronic thyroid autoimmunity; and 4) the coexistence of TgAb and TPOAb at the end of treatment is a predictive factor for the presence of thyroid dysfunction, even if subclinical, many years after IFN withdrawal.

Adult↗

Studies on thyroid cell surface antigens using cultured human thyroid cells.

Human thyroid cells in primary culture were used for studies of thyroid cell surface antibodies in patients with thyroid autoimmune disorders. Radioiodinated IgG preparations containing thyroid microsomal antibody (TMAb), thyroid stimulating antibody (TSAb) and/or thyroglobulin antibody (TgAb) were tested for binding to thyroid cells. Binding was observed with radioiodinated IgG from patients with Graves' disease, Hashimoto's thyroiditis and idiopathic myxoedema containing TMAb, irrespective of the presence of TSAb and TgAb, while negative results were obtained with normal IgG. A dose-dependent inhibition of binding to thyroid cells was produced by the addition of the corresponding unlabelled IgG preparations. Evidence for tissue specificity was provided by the absence of binding to human skin fibroblasts used as controls. Preabsorption with human thyroid microsomes completely abolished the binding to thyroid cells of a radioiodinated TMAb positive IgG preparation, while only incomplete removal of the reactivity to thyroid microsomes was produced by preabsorption with thyroid cells. These data suggest that some but not all microsomal antigenic determinants are expressed on the thyroid cell surface. Binding to thyroid cells was also observed with purified TgAb, indicating that thyroglobulin antigenic determinants are present on the surface of thyroid cells. No evidence of binding was obtained with a TSAb positive Graves' IgG preparation with undetectable TMAb and TgAb. Unlabelled IgG preparations containing TMAb from patients with either Hashimoto's thyroiditis or idiopathic myxoedema were shown to inhibit the binding to thyroid cells of radioiodinated TMAb positive Graves' IgG and vice versa. These data indicate that antibodies present in these thyroid autoimmune disorders share common thyroid cell surface antigens. However, the binding of radioiodinated IgG from a patient with idiopathic myxoedema was only partially inhibited by Graves' or Hashimoto's IgG, suggesting that some of the thyroid cell surface antibodies of idiopathic myxoedema may not be detectable in other thyroid autoimmune disorders.

Antibodies↗

[A case of acute suppurative thyroiditis associated with thyroid papillary carcinoma].

A sixty-one-year-old female was admitted to our hospital in October 1988 because of fever and a right neck mass associated with redness and tenderness. The size of the thyroid mass had gradually increased over 3 months. Two masses were detected in the thyroid by ultrasonography and MRI. She has positive thyroid autoantibodies, high CRP levels and high erythrocyte sedimentation rates. While she had normal white blood cell counts, massive neutrophils were obtained from her thyroid mass by aspiration biopsy, indicating acute suppurative thyroiditis. However, we could not find any bacteria to cause suppurative thyroiditis either in the blood or in thyroid aspirates. Serum levels of thyroid hormone were slightly elevated but she did not complain of any thyrotoxic symptoms. Radioactive iodine uptake (RAIU) of the thyroid gland was markedly decreased (2%/24h). Following treatment with antibiotics, her inflammation and symptoms immediately improved, and pus spontaneously ran from the collapsed thyroid mass. Then serum thyroid hormone levels and RAIU were normalized and the right thyroid mass disappeared. She was discharged in December 1988. There were no signs of recurrence of suppurative thyroiditis until now. She received a pharyngo-esophageal barium examination in search of the route of infection 4 times, but no fistula was revealed. However, as her left thyroid mass consistently remained thereafter, an operation of the left thyroid mass was performed in December 1989. The histologic examination of the resected thyroid revealed the coexistence of encapsulated follicular adenoma, minute papillary carcinoma and chronic thyroiditis. There are few reports of such a case having a combination of suppurative thyroiditis, thyroid cancer and chronic thyroiditis observed in an elderly female.

Acute Disease↗

Thyroid hormone for preventing of neurodevelopmental impairment in preterm infants.

BACKGROUND: Observational studies have shown an association between transiently low thyroid hormone levels in preterm infants in the first weeks of life (transient hypothyroxemia) and an abnormal neurodevelopmental outcome. Thyroid hormone therapy might prevent this morbidity. OBJECTIVES: To assess whether thyroid hormone therapy in preterm infants without congenital hypothyroidism results in clinically important changes in neonatal and long term outcomes in terms of both benefits and harms. SEARCH STRATEGY: The standard search strategy of the Neonatal Review Group was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE, previous reviews including cross references, abstracts, conferences, symposia proceedings, expert informants and journal handsearching in the English language. SELECTION CRITERIA: All trials using random or quasi-random patient allocation, in which thyroid hormone therapy (either treatment or prophylaxis) was compared to a control in premature infants. DATA COLLECTION AND ANALYSIS: Primary clinical outcomes included measures of neurodevelopmental outcome and mortality. Assessment of trial quality, data extraction and synthesis of data, using relative risk (RR) and weighted mean difference (WMD), were performed using standard methods of the Cochrane Collaboration and its Neonatal Review Group. MAIN RESULTS: Eight studies were identified that compared thyroid hormone treatment to control. Four randomized or quasi-randomized studies met inclusion criteria (Chowdhry 1984, Amato 1989, van Wassenaer 1997 and Vanhole 1997). All studies enrolled preterm infants < 32 weeks gestation, but used different timing, dose and duration of treatment with thyroid hormones. Three studies used thyroxine, whereas Amato 1989 used triiodothyronine. Only two studies with neurodevelopmental follow-up were of good methodology (van Wassenaer 1997 and Vanhole 1997). All studies were of small size with the largest, van Wassenaer 1997, enrolling 200 infants. A lack of comparability of data (neurodevelopmental test or timing of follow-up) prevented meta-analytic pooling of the studies for neurodevelopmental outcomes. There was no significant difference in mortality to discharge (typical relative risk 0.74, 95% CI 0.44, 1.26) in infants who received thyroid hormone treatment compared to controls. In individual studies, no significant differences were found in neurodevelopmental outcomes including risk of abnormal neurological outcome, and Bayley Mental or Psychomotor Development Indices. No data were available for the incidences of cerebral palsy or sensorineural impairment. Fraction of inspired oxygen was lower in infants receiving triiodothyronine in one small quasi-randomized study (Amato 1989), but not in infants receiving thyroxine in a randomized study (Vanhole 1997). No other differences were found to suggest a reduced severity of respiratory distress syndrome in infants receiving early thyroid hormone therapy. REVIEWER'S CONCLUSIONS: This review does not support the use of thyroid hormones in preterm infants to reduce neonatal mortality, improve neurodevelopmental outcome or to reduce the severity of respiratory distress syndrome. The a posteriori subgroup analyses of data from one study (van Wassenaer 1997) which showed benefits in infants 24-25 weeks gestation should be treated with caution. The small number of infants included in trials incorporated in this review limits the power of the meta-analysis to detect clinically important differences in neonatal outcomes. Future trials should be of sufficient size to detect clinically important differences in neurodevelopmental outcomes. They should consider enrolling those infants most likely to benefit from thyroid hormone treatment such as infants born at less than 27 weeks gestation and use thyroid hormones as treatment instead of prophylaxis.

Developmental Disabilities↗