Imaging in congenital hypothyroidism.

PURPOSE OF REVIEW: Congenital hypothyroidism is a common worldwide condition. Due in part to increasingly widespread newborn screening, the number of patients with this diagnosis is increasing. In this review, we discuss currently available imaging techniques and the benefits and limitations of these techniques in evaluating congenital hypothyroidism. RECENT FINDINGS: Recent work has demonstrated an increasing diagnosis of congenital hypothyroidism with normally located glands and mildly decreased thyroid function. Increasingly more genetic abnormalities have been recognized in the hormone synthesis pathways. These cases may have lower or shorter term treatment requirements than the more common severe forms of congenital hypothyroidism, and the ability to distinguish between these situations may become increasingly more important to management and counseling. SUMMARY: Imaging studies for congenital hypothyroidism may be unlikely to change immediate management in the majority of cases. The common modalities of imaging include thyroid ultrasound and radionuclide uptake scanning with either technetium or iodine. These can help establish an etiology for the condition, and in less-common causes of congenital hypothyroidism may have implications on treatment decisions, prognosis, and counseling.

Neurodevelopmental outcomes in congenital hypothyroidism: comparison of initial T4 dose and time to reach target T4 and TSH.

OBJECTIVES: To compare neurodevelopmental outcomes in severe and moderate congenital hypothyroidism (CH) among 3 different initial L-thyroxine doses and to examine the effect of the time to thyroid function normalization on neurodevelopmental outcomes. STUDY DESIGN: Neurodevelopmental assessments of 31 subjects included the Mullen Scales of Early Learning, Wechsler Preschool and Primary Scale of Intelligence-Revised, Wechsler Intelligence Scale for Children, Wide-Range Achievement Test, and Child Behavioral Checklist. RESULTS: Subjects started on higher initial L-thyroxine doses (50 mug) had full-scale IQ scores 11 points higher than those started on lower (37.5 mug) initial doses. However, verbal IQ, performance IQ, and achievement scores did not differ among the 3 treatment cohorts. Subjects with moderate CH had higher full-scale IQ scores than subjects with severe CH, regardless of the initial treatment dose. Subjects who took longer than 2 weeks to normalize thyroid function had significantly lower cognitive, attention, and achievement scores than those who achieved normal thyroid function at 1 or 2 weeks of therapy. CONCLUSIONS: Initial L-thyroxine dose and faster time to normalization of thyroid function are important to optimal neurodevelopmental outcome. In severe CH, it is important to choose an initial dose at the higher end of the recommended range to achieve these goals.

Growth hormone use in transitioning patients--clinician and payer concerns.

Determining which patients with childhood-onset growth hormone (GH) deficiency will require continuing GH therapy into and/or throughout adulthood raises clinical and economic issues, such as retesting, appropriate dosing, and the risks and benefits of uninterrupted GH treatment versus the discontinuation of therapy. In his review of the evaluation and management of patients transitioning from GH therapy in childhood to GH therapy in adulthood, Dr. Stephen LaFranchi focuses on the odds of having ongoing GH deficiency, the changes that occur when therapy is discontinued, appropriate follow up of patients who discontinue treatment, and issues regarding the reinitiation of therapy. Dr. Margaret H. MacGillivray addresses appropriate monitoring and follow up of patients in transition, as well as their classification by etiology and severity of GH deficiency. Dr. Pete Fullerton explores new issues regarding GH deficiency treatment from a managed care perspective.

Congenital hypothyroidism: etiologies, diagnosis, and management.

Congenital hypothyroidism is a common preventable cause of mental retardation. The overall incidence is approximately 1:4000; females are affected about twice as often as males. Approximately 85% of cases are sporadic, while 15% are hereditary. The most common sporadic etiology is thyroid dysgenesis, with ectopic glands more common than aplasia or hypoplasia. While the pathogenesis of dysgenesis is largely unknown, some cases are now discovered to be the result of mutations in the transcription factors PAX-8 and TTF-2. Loss of function mutations in the thyrotropin (TSH) receptor have been demonstrated to cause some familial forms of athyreosis. The most common hereditary etiology is the inborn errors of thyroxine (T4) synthesis. Recent mutations have been described in the genes coding for the sodium/iodide symporter, thyroid peroxidase (TPO), and thyroglobulin. Transplacental passage of a maternal thyrotropin receptor blocking antibody (TRB-Ab) causes a transient form of familial congenital hypothyroidism. The vast majority of infants are now diagnosed after detection through newborn screening programs using a primary T4-backup TSH or primary TSH test. Screening test results must be confirmed by serum thyroid function tests. Thyroid scintigraphy, using 99mTc or 123I, is the most accurate diagnostic test to detect thyroid dysgenesis or one of the inborn errors of T4 synthesis. Thyroid sonography is nearly as accurate, but it may miss some cases of ectopic glands. If maternal antibody-mediated hypothyroidism is suspected, measurement of maternal and/or neonatal TRB-Ab will confirm the diagnosis. The goals of treatment are to raise the serum T4 as rapidly as possible into the normal range, adjust the levothyroxine dose with growth to keep the serum T4 (or free T4) in the upper half of the normal range and the TSH normal, and maintain normal growth and development while avoiding overtreatment. An initial starting dose of 10-15 microg/kg per day is recommended; this dose will decrease on a weight basis over time. Serum T4 (or free T4) and TSH should be monitored every 1-2 months in the first year of life and every 2-3 months in the second and third years.

Severe virilization in a girl with a steroid cell tumor of the ovary.

We report a 6-year-old girl with striking signs of virilization, as well as elevated concentrations of testosterone and 17-hydroxyprogesterone. Although the elevated 17-hydroxyprogesterone concentration initially suggested late-onset 21-hydroxylase deficiency, she was found to have an ovarian mass by sonography which at surgery proved to be a hilus cell subtype of steroid cell tumor. This intra-ovarian tumor appears to be the smallest tumor of its type ever reported. The testosterone concentration was normal three days after tumor resection and has remained so two years later.

Thyroid function in the preterm infant.

Thyroid gland function develops and matures during fetal life, with production of serum thyroxine (T4) concentrations beginning around 12 weeks gestation and increasing to term. Infants born prior to term have lower cord serum T4 concentrations that correlate with gestational age or birth weight. This is partially the result of lower thyroxine-binding globulin (TBG) concentrations. The cord serum free thyroxine (FT4) concentrations also correlate with gestational age, but they are not proportionately as low as the cord T4 concentration. Preterm infants have a postnatal thyrotropin (TSH) surge and rise in serum T4 and triiodothyronine (T3), which is qualitatively similar to, but quantitatively smaller than, term infants. In contrast to term infants, preterm infants often experience a fall in serum T4 and T3 in the first week of life to below birth levels. This drop appears to be the result of many factors, including nutritional problems and decreased hepatic TBG production, immaturity of hypothalamic-pituitary control of the thyroid gland, immaturity of the thyroid gland itself, and increased tissue utilization of T4. These changes are impacted by complications of prematurity, such as respiratory distress syndrome (RDS), which result in nonthyroidal illness-like changes. Again, serum FT4 seems less affected, and when measured by equilibrium dialysis may be in the normal range for age. Several studies have correlated different measures of morbidity and mortality in the preterm infant with lower serum T4 concentrations. However, as with adults, it may be that low serum T4 concentrations are a marker of the sickest preemies. Also, as with adults, this has led to speculation that T4 treatment might be beneficial in improving these complications of prematurity, in particular the neurological outcome. While some studies appear to show improvement in some facet of medical complications with T4 treatment, most show no effect. Regarding neurological outcome, the 2 best controlled trials do not show improvement in neuropsychiatric testing outcome assessed up to 2 years of age. One study, however, showed an IQ that was 18 points higher in the T4-treated subgroup less than 27 weeks gestational age. It may be that the most preterm infants, eg, those less than 27 weeks of age, are at a disadvantage compared with their intrauterine counterparts, in that they lack the maternal thyroid hormone contribution and are forced to adapt to extrauterine life before their hypothalamic-pituitary-thyroid axis is mature enough to deal with tissue thyroxine demands. Further controlled studies are needed to determine if this subgroup of infants indeed may benefit from transient thyroid hormone supplementation.

Follow-up of newborns with low thyroxine and nonelevated thyroid-stimulating hormone-screening concentrations: results of the 20-year experience in the Northwest Regional Newborn Screening Program.

OBJECTIVES: To determine the type and frequency of thyroid disorders detected in infants with low thyroxine (T4) and nonelevated thyroid-stimulating hormone (TSH) screening test results in the Northwest Regional Newborn Screening Program (NWRNSP) over the 20-year period from May 1975 to May 1995 and to determine the effect of follow-up of these infants on the overall recall rate. STUDY DESIGN: The NWRNSP requests a serum specimen in infants with an absolute T4 level < 38.6 nmol/L (< 3 mg/dl) and in infants with two filter paper T4 concentrations less than the 3%, regardless of the TSH concentration. We conducted a retrospective analysis of infants who were followed up because of low T4 and nonelevated TSH concentrations on newborn screening. To determine the effect of follow-up of infants with low T4 levels, nonelevated TSH concentrations on the recall rate, we selected 1 year (1994) for review. Serum sample requests were evaluated to determine the reason for the request. RESULTS: Over this 20-year period, the NWRNSP detected 450 infants with primary hypothyroidism among 1,747,805 infants screened (1:3,884). Of these, 416 were detected on the basis of low T4 levels and nonelevated TSH screening test results, whereas an additional 34 infants with primary hypothyroidism and 29 infants with hypopituitary hypothyroidism were detected as a result of follow-up of low T4 levels and nonelevated TSH screening test results. This included 25 infants with delayed TSH rise (1:67,226), 9 infants with mild hypothyroidism (TSH levels < 25 mU/L) (1:194,212), 29 infants with hypopituitary hypothyroidism (1:60,269), and 434 infants with T4-binding globulin deficiency (1:4,027). Excluding those with T4-binding globulin deficiency, the false-positive rate was 43.5:1. This compares with an overall false-positive rate of 12:1 for our screening program. CONCLUSION: Follow-up of infants with low T4 and nonelevated TSH concentration on screening led to the detection of 63 additional infants with hypothyroidism, for an overall frequency of 1:27,743. We believe this yield justifies continued follow-up of infants with low T4 levels, nonelevated (TSH) screening test results in our program.

Variability of plasma cortisol levels in extremely low birth weight infants.

Cortisol is secreted by children and adults in a pulsatile pattern of 15-30 peaks and nadirs each day with a circadian rhythm. Newborns are known to lack the circadian pattern, leading to uncertainty about the appropriate time for blood sampling for assessment of adrenal function. Because extremely low birth weight (ELBW) infants may manifest signs of adrenal insufficiency, knowledge of the pattern of cortisol levels is necessary to guide the appropriate timing of blood sampling. To define the pattern of plasma cortisol levels in 14 ELBW infants, we obtained blood specimens every 20 min over a 6-h period at 4-6 days of life. Although cortisol levels in the 14 infants ranged from 2.0-54.5 micrograms/dL, each infant's cortisol levels varied little from his or her own mean cortisol level. The SDs calculated from each infant's mean cortisol level were small, ranging from 0.37-4.12 micrograms/dL. Cluster analysis was applied to the data; only 0.6 cortisol pulses/infant 6-h period were detected. Each infant's plasma cortisol levels were plotted against time, and regression analysis was performed. The slopes of the resulting lines of regression ranged from -0.0284 to 0.0221. Our data indicate that ELBW infants show little variability in their plasma cortisol levels over time; therefore, a single random measurement provides an adequate reflection of the adrenal status of the ELBW infant.

Corticosteroid binding globulin, total serum cortisol, and stress in extremely low-birth-weight infants.

Our objective was to determine if low levels of corticosteroid binding globulin (CBG) might explain the low serum total cortisol levels found in some extremely low-birth-weight (ELBW) infants. In a prospective study, serum total cortisol and CBG were measured in single blood samples from 31 ELBW infants, with a gestational age less than 28 weeks, in the first 8 days of life. Severity of illness was assessed using the Score for Neonatal Acute Physiology Perinatal Extension (SNAP-PE). The mean serum total cortisol (mean +/- 1 SD) was 9.2 +/- 9.8 mcg/mL and the mean CBG level was 1.4 +/- 0.31 mg/dL. There was no significant correlation between serum total cortisol and CBG levels (r = -0.18), severity of illness as measured by the SNAP-PE (r = +0.12), or birth weight (r = -0.12). Five of 31 infants, having a mean SNAP-PE score of 41, had serum total cortisol levels < or = 3.0 mcg/dL. Estimated mean serum free cortisol concentrations in these five infants (0.76 mcg/dL) were comparable to estimated free cortisol levels diagnostic of adrenal insufficiency in sick adult patients. Our findings indicate that CBG levels are lower in ELBW infants than in term infants, but low CBG levels do not explain the low serum total cortisol levels found in some very sick infants. Low cortisol levels in small premature infants may be adequate to support growth if the infant is well, but may result in a syndrome of adrenal insufficiency in those with severe illnesses.

Adult height in growth hormone (GH)-deficient children treated with biosynthetic GH. The Genentech Growth Study Group.

Near-adult height (AH) was determined in 121 children (72 males and 49 females) with GH deficiency (GHD) who were prepubertal when they began treatment with recombinant DNA-derived preparations of human GH. AH as a SD score was -0.7 +/- 1.2 (mean +/- SD), significantly greater than the pretreatment height SD score (-3.1 +/- 1.2), the predicted AH SD score (-2.2 +/- 1.2; Bayley-Pinneau method), and the height SD score at the start of puberty (-1.9 +/- 1.3). In contrast to studies of GH treatment outcome, which used pituitary-derived GH (pit-GH) in lower doses, we found that males did not have a higher AH SD score than females, spontaneous puberty did not diminish AH, and AH was significantly greater than that predicted at the start of GH treatment. In a multiple regression equation, the statistically significant variables (all P < 0.0001) related to AH (r2 = 0.70) were the following: duration of treatment with GH, sex (males were taller than females, as expected for the normal population), age (younger children had a greater AH) and height at the start of GH, and growth rate during first year of GH. For the AH SD score (r2 = 0.47), pretreatment predicted AH, duration of GH, and bone age delay were significant (P < 0.0002) explanatory variables. Bone age delay (chronological age-bone age) had a negative impact on the AH SD score. Target height, etiology of GHD, previous treatment with pituitary GH, and the presence or absence of spontaneous puberty did not significantly improve the prediction of AH. Early diagnosis of GHD and continuous treatment with larger doses of GH to near AH should improve the outcome in children with short stature due to GHD.

Physician and clinic charges for diagnosing growth hormone deficiency.

Physician and clinic charges for diagnosing growth hormone deficiency (GHD) in children are not generally known, whereas the charges for purchasing growth hormone (GH) are known. We recently surveyed the charges submitted to third-party payers for diagnosing GHD in five pediatric endocrine clinics throughout the United States: the Albert Einstein College of Medicine, Baylor College of Medicine, Health Science Schools of the State University of New York at Buffalo, Oregon Health Sciences University, and the University of Chicago. The financial data analyzed included charges for physician services and for GH testing. Different approaches to the medical examination of children with suspected GHD at these clinics prevented any comparison of physician or GH testing charges. However, the charges for diagnosing GHD could be determined for each pediatric endocrine clinic if the methods of examination were not considered. Contractual adjustments, net revenues, costs, and net margins were not surveyed. Subjective comments from the study sites suggest significantly reduced reimbursement amounts. We conclude that the total charges for diagnosing GHD submitted to third-party payers at these institutions averaged $1719.

Sponastrime dysplasia: five new cases and review of nine previously published cases.

Sponastrime dysplasia (SD) is a dwarfing autosomal recessive short-limb bone dysplasia. The diagnosis is established by a combination of clinical and radiological findings of which the radiological are the more specific. The current diagnostic criteria are ambiguous as demonstrated by the fact that, in our opinion, three of the five patients reported since the original article do not have this condition. Comparison of our five patients and the 9 published patients has led to development of more specific diagnostic criteria. Previously undescribed complications of this condition are subglottic stenosis and tracheo-broncho-malacia, developmental coxa vara, and avascular necrosis of the capital femoral epiphyses.

Changes in insulin-like growth factor-I (IGF-I), IGF-binding protein-3, growth hormone (GH)-binding protein, erythrocyte IGF-I receptors, and growth rate during GH treatment.

To assess the relative determinants of growth rate, we measured serum levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), and GH-binding protein (GHBP) as well as IGF-I erythrocyte receptor specific binding (SB) in 14 prepubertal GH-deficient children before and during the first year of treatment with 0.043 mg/kg.day GH. Serum IGF-I and IGFBP-3 levels, measured by RIA, were significantly increased by 2 weeks and showed progressive increases throughout the year of GH therapy. Growth rate (height velocity SD score adjusted for bone age) correlated best with the 12 month changes in IGFBP-3 (r = 0.81; P < 0.001) and IGF-I (r = 0.72; P = 0.005), and to a lesser extent with the 12 month absolute IGFBP-3 (r = 0.58; P = 0.04) and the 6 month change in IGFBP-3 (r = 0.55; P = 0.05). The baseline IGF-I correlated inversely with the growth rate during GH therapy (r = -0.55; P = 0.05) and was the best pretreatment predictor of growth response. GHBP, as measured by ligand-mediated immunofunctional assay, showed no significant change during GH therapy and did not correlate with growth response. The baseline GHBP, however, did correlate with both the 12 month IGFBP-3 (r = 0.72; P = 0.006) as well as the 2 week change in IGFBP-3 (r = 0.63; P = 0.05). Erythrocyte IGF-I SB showed a significant decrease by 6 months secondary to a decrease in IGF-I receptor number, with no change in affinity. The 6 month IGF-I receptor binding correlated inversely with the increase in IGF-I (r = -0.88; P < 0.001). Erythrocyte IGF-I SB at baseline did not correlate with the growth response, although there was an inverse trend between the 6 month IGF-I receptor level and the growth rate. IGF-I and IGFBP-3 show progressive increases, whereas the erythrocyte IGF-I receptor-binding capacity decreases by 6 months, and GHBP shows little change during the first year of GH treatment. Data from this study suggest that changes in IGFBP-3 and, to a lesser extent, IGF-I are the major correlates of growth rate, and that down-regulation of the IGF-I receptor may have relatively little influence on growth rate compared with changes in IGFBP-3 and IGF-I.

Activating mutation in the stimulatory guanine nucleotide-binding protein in an infant with Cushing's syndrome and nodular adrenal hyperplasia.

Cushing's syndrome in infancy is uncommon. In this report, we describe an infant with ACTH-independent Cushing's syndrome in which an activating mutation in the stimulatory G-protein (Gs alpha) was detected. The patient presented at 3 months of age with Cushingoid features, poor linear growth, and elevated liver enzymes. Plasma ACTH and dexamethasone suppression test results were consistent with ACTH-independent Cushing's syndrome, and a subsequent adrenalectomy revealed bilateral adrenocorticonodular hyperplasia. Asymptomatic lesions consistent with fibrous dysplasia were later detected on bone scan. Genomic DNA was extracted from adrenal, liver, and blood and amplified by polymerase chain reaction with Gs alpha exon 8 primers. Using allele-specific oligonucleotide hybridization, the DNA was probed for known Gs alpha-activating mutations. A point mutation coding for an arginine to cysteine substitution at codon 201 of exon 8 was detected in genomic DNA from this infant's adrenal, liver, and leukocytes. The mutation was detected in nodular adrenal tissue, but was essentially absent in normal adrenal tissue. Activating mutations in the Gs alpha gene have previously been described in GH-secreting tumors, thyroid adenomas, and the McCune-Albright syndrome and are probably involved in the pathogenesis of adrenocorticonodular hyperplasia in this infant with Cushing's syndrome.

Adolescent Thyroid Disorders.

Thyroid disorders are common in adolescents; in fact, they occurred in 3.7% of children between the ages of 11 and 18 in one study. Early recognition and treatment of these conditions can help to minimize their effects. Here, the author details the epidemiology, diagnosis, and clinical management of hypothyroidism, hyperthyroidism, thyroid nodules, and cancer.

Hypothalamic pituitary adrenal function in the extremely low birth weight infant.

Extremely premature infants manifest clinical features suggestive of adrenal insufficiency. Yet, serum cortisol levels are similar in ill and well preterm infants in a setting where one would expect high stress levels in the ill infants. We investigated the hypothalamic-pituitary-adrenal axis in 17 extremely low birth weight stressed premature infants, mean birth weight 739 g, gestational age, 26.1 weeks, using ovine CRH (oCRH) and ACTH stimulation. oCRH (1 microgram/kg) was administered at 2-7 days of life (mean = 4.1). ACTH rose from a basal value 6.0 +/- 0.8 pmol/L (mean +/- SEM) to 9.6 +/- 1.8 pmol/L (P < 0.01) at 15 min and 9.5 +/- 1.7 pmol/L (P < 0.01) at 60 min. Basal cortisol rose from 349.3 +/- 58.1 nmol/L to 422.3 +/- 57.9 nmol/L (P < 0.01) at 15 min and 568.7 +/- 60.2 nmol/L (P < 0.01) at 60 min. Cortisol values remained significantly (P < 0.05) elevated 24 h after oCRH. An ACTH stimulation test performed 24 h after the oCRH test demonstrated a significant cortisol rise from 603.5 +/- 130.5 nmol/L to 882.7 +/- 136.6 nmol/L (P < 0.05) at 60 min. Plasma CRH immunoactivity was also measured before oCRH testing and was detectable in 10 of 15 infants. The mean CRH immunoactivity was 21.8 +/- 4.4 pmol/L in the infants, significantly higher than 8 adult male controls (P < 0.04). Our results show a normal pituitary response to ovine CRH and a normal adrenal response to ACTH. We hypothesize that cortisol levels are inappropriately low in some ill preterm infants because of the inability of the extremely premature brain to recognize the stress of the illness or because of inadequate hypothalamic secretion of CRH. The significance of the measurable plasma CRH in the first week of life is unknown.

Thyroxine-binding globulin deficiency detected by newborn screening.

We examined the results of the Northwest Regional Screening Program from May 1975 to June 1991 to determine the prevalence of inherited thyroxine-binding globulin (TBG) deficiency and its effect on thyroid hormone concentrations in infants. Serum thyroxine (T4), triiodothyronine resin uptake (T3RU), and thyrotropin values were requested of physicians caring for all infants with a single filter paper T4 level < 38.6 nmol/L (3 micrograms/dl) or a T4 level < 3rd percentile on two filter paper tests (at birth and 2 to 6 weeks of age). From 1,367,724 infants screened in five states, TBG deficiency, an X-linked disorder, was identified in 317 infants (285 boys). For the entire screening program the calculated frequency of TBG deficiency was 1:4315 infants (1:2400 for boys). In Oregon, where 95% of infants have two screening tests performed, the calculated frequency was somewhat higher (1:3080 infants; 1712 boys) and is probably more accurate. The mean serum T4 concentration for TBG-deficient boys was 41.9 nmol/L (3.26 micrograms/dl); 31% had values < 25.7 nmol/L (2.0 micrograms/dl). The mean serum T4 concentration for TBG-deficient girls was 60.2 nmol/L (4.68 micrograms/dl), with none < 2.0 micrograms/dl. The mean T3RU value was 0.472 in TBG-deficient boys, and 0.412 in TBG-deficient girls; the T3RU value was > 0.55 in 24% of TBG-deficient boys but was > 0.55 in only one girl. Free serum T4 levels were normal in all 56 TBG-deficient infants studied, and TBG levels were low in all 20 infants studied. Inherited TBG deficiency is common in boys in the Northwest, with a frequency of 1:1700 and a male/female ratio of 8.9:1. Boys with TBG deficiency have mild, moderate, or severe alterations in total T4 and T3RU values, but severe deficiency is rare in girls.