Neuropsychological study in treated thyroid dysgenesis

[Newborn screening for congenital hypothyroidism and congenital adrenal hyperplasia: Benefits and costs of a successful public health program]

Newborn screening is an important public health program and a triumph of preventive medicine. Economic analyses show that the benefits of newborn screening clearly outweigh the costs for certain diseases, but not necessarily for other ones. This is due to the great diversity of the natural history of the diseases detected, to the fact that each of these diseases considered individually is rare, and to differences in the effectiveness of interventions. In addition, the benefit-cost ratio of screening for a particular disorder may differ between countries, specifically between high-income and low- and middle-income countries. The burden of a disorder may also be alleviated by increased clinical awareness and effective clinical services, even in the absence of newborn screening. In this article, we focus on economic analyses of newborn screening for primary congenital hypothyroidism, which has been in place in high-income countries for roughly 40 years, and for classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Screening for the latter is not yet universal, even in high-income countries, although the lack of universal implementation may reflect factors other than economic considerations.

Differences in the auxological characters of children with short stature - Differential diagnostic possibilities of hypothyreosis

This study aimed to define the differences in growth characteristics in the three most frequent causes of growth retardation - growth hormone deficiency, hypothyreosis and constitutional delay of growth and development - in order to provide diagnostic means for distinguishing these disorders. The study included 166 children with growth disorders aged 4-18 years. The height for age, the bone age using the TW3 method, the predicted height as the target height and the current prediction using the TW3 method were studied. For bone age, the radius, ulna and short bones compartment (RUS) and carpal bones (CARP) were evaluated separately and the difference in their delay in relation to chronological age (ΔBA_RUS_CARP) was determined. The relationship of the studied variables with sex and the underlying diagnosis was tested and the relationship of hypothyreosis and growth data was estimated. The model was tested on the growth data of 104 randomly selected patients with a growth disorder. The largest significant distinction was demonstrated by the difference ΔBA_RUS_CARP in hypothyreosis. The created linear regression model was highly statistically significant (χ² = 19.4, p < 0.0001) and showed high selectivity (0.609, 95% CI 0.409; 0.808) as well as high specificity (0.864, 95% CI 0.781; 0.946). The clinical validity of the model demonstrated a 61% predictive value for the detection and an 81% successful specification of hypothyreosis. The study demonstrated the possibility of distinguishing suspected hypothyreosis from other causes of growth retardation based on differences in severity of the ossification delay in skeletal compartments of the hand.

Hypothyroïdie congénitale

Congenital hypothyroidism is the principle cause of preventable mental retardation, with a prevalence of 1 in 3,500 neonates. The disorder may be permanent or transitory. Permanent congenital hypothyroidism is caused principally by thyroid dysgenesis. In industrialized countries, mass screening allows the disorder to be diagnosed at birth. The severity is variable but is generally more pronounced in females. The majority of studies point to a genetic origin for the disease and no consistent evidence has been found to suggest a major role for environmental factors. The genetic factors have already been identified and involve several elements (mutations in the TTF-1, TTF-2, PAX8 and TSH receptor genes). The etiological diagnosis is based on scintigraphy, ultrasound and the level of circulating thyroglobulin. At present, treatment is administered at an adapted dose during the first two weeks of life and should allow the child to reach its full intellectual potential. However, minor anomalies have been reported in some treated children, suggesting that this treatment cannot compensate for a certain degree of foetal hypothyroidism.

Cognition and behavior at school entry in children with congenital hypothyroidism treated early with high-dose levothyroxine

OBJECTIVE

To document cognition and behavior at school entry in these patients. Study design Eighteen children with congenital hypothyroidism (CH; 9 severe and 9 moderate, based on a surface of the knee epiphyses at diagnosis<or >or=0.05 cm(2)) treated from a median of 14 days with a median of 12.0 microg/kg per day of levothyroxine were evaluated at 5 years, 9 months, with the McCarthy Scale and the Questionnaire for Evaluation of Social Behavior, as were 40 control children.

RESULTS

The global IQs at 5 years, 9 months, were similar: medians (range) were 102 (87 to 133), 102 (84 to 135), and 115 (88 to 136) (not significant) for severe CH, moderate CH, and control children, respectively. The behavioral scores of CH children were within the normal range. However, the number of times when plasma TSH was >6.0 mIU/L during treatment was correlated positively with anxiety (P=.02) and inattention (P=.05), whereas the number of times TSH was <0.8 mIU/L was correlated with lower verbal scores (P=.05).

CONCLUSIONS

Children with severe CH treated early with a high dose of levothyroxine have normal global development and behavior at school entry.

Screening for neonatal endocrinopathies: rationale, methods and results

The measurement of thyrotropin or thyroxine from dried blood spots collected from neonates allows diagnosis before clinical manifestations develop, and prevents mental deficiency from congenital hypothyroidism. However, severely hypothyroid newborns remain at risk of cognitive problems that may be avoided if they are treated within two weeks of birth, hence the importance of a quick turnaround time of the screening programme. This also applies to screening for congenital adrenal hyperplasia due to 21-hydroxylase deficiency based on the measurement of 17-hydroxy-progesterone from dried blood; this was primarily designed to prevent neonatal deaths from acute adrenal insufficiency. This goal can be achieved by a high degree of clinical awareness of the diagnosis, but this has only been reported in a few jurisdictions. Furthermore, biochemical screening allows earlier treatment. On the other hand, there are many false positives, mostly in premature infants, so screening for 21-hydroxylase deficiency has not been universally adopted.

Treatment for congenital hypothyroidism: thyroxine alone or thyroxine plus triiodothyronine?

OBJECTIVE

To compare the effects of therapy with thyroxine (T4) plus triiodothyronine (T3) versus T4 alone from the first days of life in screened congenital hypothyroid (CH) infants.

METHODS

We examined 14 CH infants diagnosed by neonatal screening and a group of control infants. CH patients were divided randomly into 2 groups, 1 treated with T4 alone (group 1) and the other treated with T4 plus T3 (liothyronine; group 2). In all patients electrocardiography and thyroid hormone evaluations were performed before and 15 and 30 days and 3, 6, and 12 months after the beginning of therapy. Psychological tests were also performed at 6 and 12 months of age in CH patients and in other matched controls.

RESULTS

After 15 days of treatment, serum thyrotropin (TSH) levels become normal in 5 of 7 cases of group 1 (median TSH level 10.7 micro U/ml) and in 1 of 7 cases of group 2 (median TSH level 72.5 micro U/ml). At the same period, serum-free thyroid hormone levels were within the normal range in both groups, but free T4 values were significantly higher in group 1 than in group 2 and in controls. At the subsequent examinations, free T4 values were within the upper normal limit in group 1, whereas they remained within the normal range in group 2. No clinical or electrocardiographic signs of heart disease were found in any of the patients. The psychometric quotient in CH infants was significantly lower than in controls, but similar in patients of group 1 and group 2.

CONCLUSIONS

The combined treatment with T4 plus T3 seems not to show significant advantages, at least in our experimental conditions, compared with the traditional treatment with T4 alone in early treated CH infants. A further longer and more extensive follow-up is mandatory.

Auditory brainstem evoked potentials in early-treated congenital hypothyroidism

To evaluate the effect of early treatment of congenital hypothyroidism on central nervous system development, auditory brainstem evoked potentials were determined in 32 patients with hyperthyrotropinemia diagnosed during neonatal screening. The patients included 27 with congenital hypothyroidism and 5 with transient hypothyroidism. Abnormal auditory brainstem evoked potential tracings were found in 8 patients (congenital hypothyroidism in 7 and transient hypothyroidism in 1). Four of these patients had increased peripheral conduction time (wave I prolongation), and the other 4 had increased central conduction time (wave III or V prolongation). The patients with abnormal auditory brainstem evoked potentials did not show increased initial manifestations, yet 6 of them had lower initial thyroxine levels. Specific auditory brainstem evoked potential abnormalities were found in 25% of early-treated patients with congenital hypothyroidism. The possible causal relationship between deviant auditory brainstem evoked potential patterns and later neurodevelopment demands further clarification. This study suggests the usefulness of auditory brainstem evoked potential assessment to provide information about electrophysiologic deviation of the auditory pathway in patients with early-treated congenital hypothyroidism.

Children with irreversible brain damage associated with hypothyroidism and multiple intracranial calcifications

Children who develop clinical hypothyroidism in early childhood have various degrees of irreversible brain damage, albeit less severe than cases detected by neonatal screening test for hypothyroidism in the first months of the life. We report three patients with hypothyroidism of childhood onset after a normal neonatal thyroid-stimulating hormone screening who showed deceleration in linear growth, spasticity in the lower limbs with deformity, mild intellectual impairment, and multiple calcifications in the basal ganglia and subcortical areas. The neurologic symptoms were not progressive but were irreversible in spite of thyroxine treatment. Motor disturbances commonly observed in postnatal-onset hypothyroidism are similar to those of cerebral palsy. Specific distribution of intracranial calcifications may result from metabolic derangement as a result of hypothyroidism, although the mechanism of calcification is not fully understood. We emphasize the need to re-evaluate thyroid function in diplegic patients with specific intracranial calcifications but normal neonatal thyroid-stimulating hormone screening.

The potential repercussions of maternal, fetal, and neonatal hypothyroxinemia on the progeny

The adequate functioning of both the maternal and fetal thyroid glands play an important role to ensure that the fetal neuropsycho-intellectual development progresses normally. Three sets of clinical disorders are considered, that may eventually lead to impaired brain development. Firstly, in infants with a defect of glandular ontogenesis (congenital hypothyroidism), the participation of maternal thyroid hormones to the fetal circulating thyroxine environment is normal and, therefore, risk of brain damage results exclusively from the insufficient hormone production by the abnormal fetal thyroid gland. Secondly, when it is only the maternal thyroid gland that is functionally deficient (autoimmune hypothyroidism), the severity and temporal occurrence of maternal underfunction will both drive the resulting consequences for impaired fetal neuronal development. Clinical situations of this type may obviously take place already during early gestation (in women with known but untreated hypothyroidism) or appear only during later gestational stages (in women who have AITD and remain euthyroid during the first half of gestation). Lastly, in conditions with iodine deficiency, both maternal and fetal thyroid functions are affected and, therefore, it is primarily the degree and precocity of the maternal hypothyroxinemia due to iodine deficiency during pregnancy that will drive the potential repercussions for fetal neurological development. In the present review, we summarize available data and develop our present concepts concerning the complex feto-maternal thyroid relationships and the potential impacts of thyroid function abnormalities on the ideal development of the offspring.

[Results of national evaluation tests (primary schools) of CE2 and 6th classes of 73 students with congenital hypothyroidism screened at birth]

Assessment of school performance provides an excellent index of adequacy of therapy of congenital hypothyroidism.

PATIENTS AND METHODS

Scholarly achievement of 73 children with congenital hypothyroidism screened and followed-up in our clinic was evaluated by comparison to national tests calculated from a wide random sample. The 73 children were divided into three groups: 31 patients belonging to the CE2 class (third primary school class) (group 1); 13 patients belonging to the 6th class (first secondary school class) having already passed CE2 tests (group 2); and 16 patients also belonging to the 6th class but not having passed CE2 tests (group 3).

RESULTS

The youngest patients showed better results in French than national means, with similar results in mathematics. The intermediate aged patients showed comparable scores to the national mean in both tests. The oldest patients showed significantly less achievement in mathematics, and somewhat (but not markedly) less achievement in French. Etiology of hypothyroidism did not seem to be a prognostic factor, with the athyreotic patients having better results in CE2 than ectopic ones. Age at onset of treatment and the duration of treatment before normalization of thyroid stimulating hormone (TSH) seemed to represent the main prognostic factors as does compliance to treatment, which depends on socioeconomic levels of families.

CONCLUSION

Encouraging results are now obtained in those patients who have been screened in the neonatal period and treated very early. Compliance to the treatment remains an important factor of prognosis.

Anterior pituitary function during critical illness and dopamine treatment

OBJECTIVE

To summarize the available data on anterior pituitary function in critical illness and to focus on the endocrine effects of dopamine infusion. The analogy with anterior pituitary function in the elderly is highlighted, and the potential importance of these observations for recovery from critical illness is discussed.

DATA SOURCES

Computerized search of published research and reference list review.

STUDY SELECTION

Review of 178 citations. Included are seven original studies on the effect of dopamine on pituitary function in adult and pediatric critical illness performed by the authors.

DATA EXTRACTION

Studies on the endocrinology of illness, chronic stress, aging, and dopamine, or on the clinical importance of endocrine changes.

DATA SYNTHESIS

The different pituitary axes are important determinants of normal anabolism and immune function. Continuously increased serum cortisol concentrations, insulin resistance, blunted prolactin release, and attenuated pulsatility of growth hormone and luteinizing hormone secretory patterns, as well as multiple anomalies in the thyroid axis, characterize the endocrine profile of prolonged critical illness. Dopamine, a natural catecholamine with hypophysiotropic properties, which has been used for more than two decades as an inotropic and vasoactive drug in intensive care, suppresses the circulating concentrations of all anterior pituitary-dependent hormones, except for cortisol. Available evidence suggests that the major effect of dopamine administration on the endocrine system is unlikely to be beneficial for the threatened metabolic and immunologic homeostasis of the severely ill patient. This pattern of hypopituitarism induced by chronic, severe illness and exogenous dopamine administration is reminiscent of the hormonal profiles obtained in experimental models of chronic stress, suggesting that endogenous dopamine may play a role in the endocrine and metabolic response to critical illness.

CONCLUSIONS

The dopamine-induced or aggravated pituitary dysfunction in critical illness warrants caution with prolonged infusion of this catecholamine as a so-called supportive agent, particularly in early life. The potential of combined hormonal therapy to improve the metabolic and immune status of the critically ill patient deserves thorough investigation.

Biology of the congenitally hypothyroid hyt/hyt mouse

The hyt/hyt mouse has an autosomal recessive, fetal onset, characterized by severe hypothyroidism that persists throughout life and is a reliable model of human sporadic congenital hypothyroidism. The hypothyroidism in the hyt/hyt mouse reflects the hyporesponsiveness of the thyroid gland to thyrotropin (TSH). This is attributable to a point mutation of C to T at nucleotide position 1666, resulting in the replacement of a Pro with Leu at position 556 in transmembrane domain IV of the G protein-linked TSH receptor. This mutation leads to a reduction in all cAMP-regulated events, including thyroid hormone synthesis. The diminution in T3/T4 in serum and other organs, including the brain, also leads to alterations in the level and timing of expression of critical brain molecules, i.e. selected tubulin isoforms (M beta 5, M beta 2, and M alpha 1), microtubule associated proteins (MAPs), and myelin basic protein, as well as to changes in important neuronal cytoskeletal events, i.e. microtubule assembly and SCa and SCb axonal transport. In the hyt/hyt mouse, fetal hypothyroidism leads to reductions in M beta 5, M beta 2, and M alpha 1 mRNAs, important tubulin isoforms, and M beta 5 and M beta 2 proteins, which comprise the microtubules. These molecules are localized to layer V pyramidal neurons in the sensorimotor cortex, a site of differentiating neurons, as well as a site for localization of specific thyroid hormone receptors. These molecular abnormalities in specific cells and at specific times of development or maturation may contribute to the observed neuroanatomical abnormalities, i.e. altered neuronal process growth and maintenance, synaptogenesis, and myelination, in hypothyroid brain. Abnormal neuroanatomical development in selected brain regions may be the factor underlying the abnormalities in reflexive, locomotor, and adaptive behavior seen in the hyt/hyt mouse and other hypothyroid animals.

Childhood IQ measurements in infants with transient congenital hypothyroidism

OBJECTIVE

In view of the fact that, during the first period of life, thyroid hormones are critical for brain development, we investigated whether even transient congenital hypothyroidism could affect the long-term intellectual development of affected infants.

DESIGN

A case-control study of intellectual development, auxometric parameters and thyroid function performed in late infancy in children with documented transient congenital hypothyroidism or hyperthyrotrophinaemia at birth.

PATIENTS

Nine children born in an endemic goitre area who had short-term transient congenital hypothyroidism or hyperthyrotrophinaemia after birth (TCH) were studied and compared to nine matched children born in the same area at the same time but having normal thyroid function at birth (N).

MEASUREMENTS

Global, verbal and performance IQs were evaluated on the Wechsler scale. Height, bone age, total and free thyroid hormones, thyroid volume, thyroglobulin, basal and TRH stimulated TSH were also measured.

RESULTS

Height and bone age were similar in the two groups. Thyroid function tests were also similar in the two groups except for basal and TRH stimulated serum TSH and serum Tg which were higher in the TCH than in the control group. Global, verbal and performance IQs were systematically lower in the TCH than in the N group. (78.3 +/- 11.1 vs 90.9 +/- 14.2, P < 0.05; 84.4 +/- 15.4 vs 96.2 +/- 14.8, P NS; 75.0 +/- 8.5 vs 89.2 +/- 12.5, P < 0.01 respectively).

CONCLUSION

Infants born and living in an academic goitre area, who had biochemical signs of thyroid hypo-function at birth, had a lower intelligence quotient at the age of 7-8 years than matched controls living in the same environmental conditions but with normal thyroid function at birth. The present findings strongly suggest that abnormalities in thyroid function at birth, even when transient, can adversely affect long-term intellectual development.

Congenital hypothyroidism--correlation between radiographic appearances of the knee epiphyses and biochemical data

Plain knee radiographs of 20 neonates with congenital hypothyroidism, were reviewed. The size and appearances of the epiphyses were compared with the biochemical data at the time of referral. Fifteen infants had unequivocal evidence of delayed bone maturation based on absence of the distal femoral epiphysis or small epiphyseal size. Seven cases had fragmentation of at least one epiphysis. A positive correlation was found, at diagnosis, between the thyroxine and triiodothyronine levels and the size of the knee epiphyses. All 14 infants with thyroxine levels of less than 70 nmol/l had small epiphyses with a combined mean diameter of the proximal tibial plus distal femoral epiphyses of 7 mm or less. Conversely, of the 6 infants with thyroxine levels of 70 nmol/l or above, 5 had combined epiphyseal diameters of greater than 10 mm. We suggest that in infants with no clinical symptoms and only moderately raised raised screening thyroid stimulating hormone, a knee radiograph showing the described radiological changes should prompt institution of thyroxine treatment before awaiting biochemical confirmation of the diagnosis.

Congenital hypothyroidism, as studied in rats. Crucial role of maternal thyroxine but not of 3,5,3'-triiodothyronine in the protection of the fetal brain

To study the protective effects of maternal thyroxine (T4) and 3,5,3'-triiodothyronine (T3) in congenital hypothyroidism, we gave pregnant rats methimazole (MMI), an antithyroid drug that crosses the placenta, and infused them with three different doses of T4 or T3. The concentrations of both T4 and T3 were determined in maternal and fetal plasma and tissues (obtained near term) by specific RIAs. Several thyroid hormone-dependent biological end-points were also measured. MMI treatment resulted in marked fetal T4 and T3 deficiency. Infusion of T4 into the mothers increased both these pools in a dose-dependent fashion. There was a preferential increase of T3 in the fetal brain. Thus, with a T4 dose maintaining maternal euthyroidism, fetal brain T3 reached normal values, although fetal plasma T4 was 40% of normal and plasma TSH was high. The infusion of T3 pool into the mothers increased the total fetal extrathyroidal T3 pool in a dose-dependent fashion. The fetal T4 pools were not increased, however, and this deprived the fetal brain (and possibly the pituitary) of local generation of T3 from T4. As a consequence, fetal brain T3 deficiency was not mitigated even when dams were infused with a toxic dose of T3. The results show that (a) there is a preferential protection of the brain of the hypothyroid fetus from T3 deficiency; (b) maternal T4, but not T3, plays a crucial role in this protection, and (c) any condition which lowers maternal T4 (including treatment with T3) is potentially harmful for the brain of a hypothyroid fetus. Recent confirmation of transplacental passage of T4 in women at term suggests that present results are relevant for human fetuses with impairment of thyroid function. Finding signs of hypothyroidism at birth does not necessarily mean that the brain was unprotected in utero, provided maternal T4 is normal. It is crucial to realize that maintainance of maternal "euthyroidism" is not sufficient, as despite hypothyroxinemia, the mothers may be clinically euthyroid if their T3 levels are normal.

The value of neonatal serum thyroglobulin determinations in the follow-up of patients with congenital hypothyroidism

Serum thyroglobulin was determined in 68 newborn infants with positive screening tests for congenital hypothyroidism. In 38 infants the diagnosis was confirmed (patients), but the remaining 30 were euthyroid at follow-up (controls). The mean thyroglobulin concentration at the age of 2 weeks did not differ significantly between the patients and the controls (179 vs. 125 micrograms/l). Thyroid scintigraphy was performed in 15 patients. All seven with thyroid aplasia, based on 99mTc pertechnetate scintigraphy, had measurable thyroglobulin (greater than 2 micrograms/l) and thyroid hormones in their serum. This indicates that total absence of thyroid tissue is very rare in Swedish patients with congenital hypothyroidism. Scintigraphy based on 99mTc does not permit detection of small amounts of thyroid tissue. The neonatal concentrations of thyroglobulin did not correlate with the results of Griffiths test at 3 years and are therefore not useful for prognosis of psychomotor development. We conclude that neonatal measurement of thyroglobulin is of limited value in the follow-up of patients with congenital hypothyroidism.

Congenital hypothyroidism: physiological and psychological factors in early development

Children diagnosed as congenitally hypothyroid and treated from a very early age were followed up at 1 and 3 years. At 1 year they seemed to be developing normally, unless they were undertreated or had an additional disorder. There were no significant correlations between biochemical or social factors and psychological outcome at 1 year. At 3 years, however, those children whose T4 and/or T3 had been very low initially had significantly lower IQ scores than both other hypothyroid children and matched controls. Children with only moderately low initial T4 and/or T3, however, were doing just as well as their matched controls. Initial levels of TSH, the number of symptoms at first clinical interview and the age at the start of treatment were not good indicators of ability at 3 years. Undertreatment was rare but did appear to affect ability. Psychological outcome at 3 years was also correlated with social class (for both cases and controls). Multiple regression analyses indicated that both low initial T4 (less than 20 nmol/l) and social class contributed significantly to outcome.

Multivariate analysis of psychomotor development in congenital hypothyroidism

In the Finnish programme of screening for congenital hypothyroidism (CHT), thyroid replacement therapy is started very early (at a median age of 6 days). Our experience with the first 50 patients detected by this programme confirms that clinically relevant mental retardation is avoided by early therapy. But some intrauterine damage is inevitable and its degree correlates with the severity of the CHT. Age at the start of therapy, in our narrow range, did not appear to influence the outcome, as we found only a paradoxical positive correlation between the two. Our results suggest that thyroid hormone is transferred from the mother to her hypothyroid child during delivery.

Bone age at birth; method and effect of hypothyroidism

Bone maturity at birth (or during the neonatal period) can be estimated from the ossified distal femoral epiphyses (FE). In congenital hypothyroidism (CHT) bone maturation is retarded and neonatal bone age reflects the severity of prenatal thyroid failure. In our reference group of 111 healthy infants, the size of these epiphyses depended not only on the age but also on body size. Thus, if bone age is estimated from the size of an epiphysis, the size of the infant is a potential confounder. This problem was avoided by estimating the maturation lag from the difference between the observed and predicted heights of FE (FEHs). Models for predicting FEH were constructed from data from the reference group by multiple linear regression and confirmed in a separate group of 37 healthy infants. In 52 hypothyroid newborns both FEH and FEH lag correlated with serum thyroxine concentration, indicating that FEH can be used as a measure of bone maturation in a population that is fairly homogeneous for (postmenstrual) age and size. Otherwise FEH lag is a better indicator.

Thyroid hormone resistance in a large kindred: physiologic, biochemical, pharmacologic, and neuropsychologic studies

PURPOSE

Thyroid hormone resistance affects the pituitary gland and a variety of other tissues. We studied a large kindred with this disorder and measured a number of clinical markers of tissue metabolism to determine if these markers were useful in elucidating the sites and degree of resistance.

PATIENTS

A kindred of 89 persons in four generations was identified; 44 had thyroid function tests, and 14 (five to 67 years old) were found to have thyroid hormone resistance.

RESULTS

The inheritance pattern was autosomal dominant, with no common HLA haplotype. Physiologic measurements in five affected members showed marked heterogeneity. Four patients had normal baseline cardiac contractility, but only two experienced a shortening of their QKd interval into the hyperthyroid range with triiodothyronine (T3) therapy. Intrathyroidal 127I content was increased in two patients and was normal in two. Bone mineral content was normal in two men, but two women had marked osteopenia. The propositus, hypothyroid after inappropriate 131I therapy, had a hypothyroid ventilatory response to hypercapnea. This response became low normal during T3 (100 micrograms/day) administration but not during long-term thyroxine (T4) (300 micrograms/day) administration. Three other patients had values within normal limits and one had a hyperthyroid ventilatory response. Peripheral biochemical markers of thyroid hormone action were measured in 13 affected and 19 unaffected family members. Sex hormone-binding globulin was increased in zero of 13 affected patients (versus 19 of 20 hyperthyroid, chi 2:p less than 0.001); ferritin was elevated in two of 13 patients (versus 11 of 20 hyperthyroid, p less than 0.02); angiotensin converting enzyme activity was increased in one of 13 patients (versus 12 of 20 hyperthyroid, p less than 0.025). The eldest patient had marked cardiac sensitivity despite normal biochemical markers. We attempted to suppress the integrated thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) using T3 (72 and 100 percent suppression in two patients), dopamine (40 percent suppression in one), 3,5,3'-triiodothyroacetic acid (TRIAC) (94 percent suppression in one), and verapamil (10 percent and 40 percent suppression in two). Neuropsychologic function was studied in 14 individuals (11 affected, three unaffected). Although mild impairments were detected, they were not specific for thyroid hormone resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurological consequences of congenital hypothyroidism in Fischer 344 rats

Congenital hypothyroidism was induced in rat pups by treating pregnant and lactating dams with an antithyroid drug, methimazole. Methimazole (0.00, 0.01, 0.03 or 0.10 mg/ml) was added to the drinking water of female Fischer 344 rats from gestational day 17 through lactational day 10. The same animals as pups and adults were evaluated with a developmental neurotoxicological test battery. Pups were evaluated for physical measures of maturation, thermoregulation, flash evoked potential (FEP), motor activity, and morphology of brain, thyroid and kidneys. Parameters evaluated in the same animals as adults were body weight, functional observational battery, grip strength, body temperature, and neurological tests (FEP, auditory brainstem response to 4 and 16 kHz tone pips (ABR4, ABR16) and clicks (ABRc), somatosensory evokes potentials recorded from the somatosensory cortex (SEP-S) and the cerebellum (SEP-C), and caudal nerve action potential to single and paired stimuli (CNAP). Treatment-related findings in pups included slightly decreased body weight, slightly increased kidney weights, altered thyroid morphology, delayed incisor eruption, decreased thermoregulation, and FEP changes. Although a pup no effect level was not determined, effects at 0.01 mg/ml were minimal. Adult ABR4 and ABR16 waveforms were slower than controls and had altered shapes; ABRc, SEP-S, and SEP-C waveforms exhibited reduced power, increased latency and altered shape. Effects were detected in adults at all doses and thus, the neurological characteristics of rat congenital hypothyroidism were clearly detected with this developmental neurotoxicological test battery. The effects on body weight, kidney weight and thyroid morphology, however, suggest a general developmental effect and nervous system function did not appear to be preferentially affected.

Neonatal hypothyroidism: recent developments

This chapter summarizes recent developments in the field of sporadic congenital hypothyroidism (CH) and transient neonatal hypothyroidism detected by systematic neonatal thyroid screening. The incidence of CH detected by screening is about 1 in 4000 births in North America, Europe and Australia; it is lower (1 in 7000) in Japan. The aetiology remains unknown; genetic and environmental factors are possibly involved. The role of autoimmunity has recently been studied extensively. Antithyroglobulin (ATA) and antimicrosomal antibodies are not involved; the possible role of thyroid growth blocking antibodies (TGBAb) of maternal origin remains controversial. Evaluation of clinical signs, bone maturation, serum T4 and the position and size of the thyroid by scintigraphy at the time of diagnosis in CH infants are important because these variables are related to the final psychoneuro-intellectual prognosis, irrespective of the adequacy of therapy. Thyroid echography always distinguishes a normal thyroid in the neonate but cannot define precisely the type of thyroid dysgenesis, if present (e.g. ectopic, athyreosis). The determination of serum Tg contributes to the diagnosis but its specificity and sensitivity are insufficient to replace thyroid scintigraphy. Therapy by LT4, at an initial dose of 25-50 micrograms/day in full-term infants, is universally recommended. The objective of therapy is to reach as soon as possible and to maintain serum concentrations of total and free T4 at the upper limits of normal for age. Serum TSH should decrease as rapidly as possible below 20 microU/ml and then remain within the normal range. Persistent hyperthyrotropinaemia in spite of normal serum T4 has to be avoided as it could represent poor compliance and/or insufficient therapy. Programmes of 10 to 14 years of follow-up of CH infants have now shown that the neuropsychointellectual prognosis of CH is excellent in all cases when therapy and psychosocial environment are adequate. Although still within the normal range, IQ is somewhat lower in spite of appropriate therapy in cases of severe prenatal hypothyroidism and some transient and correctable neurological signs occasionally occur. In Western countries transient neonatal hypothyroidism is usually due to iodine deficiency or iodine excess; the newborn infant is hypersensitive to the antithyroid action of an extraphysiological supply of iodine. TSH binding inhibitor immunoglobulins (TBII) of maternal origin occasionally cause transient neonatal hypothyroidism. In developing countries with severe iodine deficiency and endemic goitre, the incidence of thyroid failure in the newborn can be as high as 1 in 10.(ABSTRACT TRUNCATED AT 400 WORDS)

Manifestations of congenital hypothyroidism during the 1st week of life

Congenital hypothyroidism (CHT) produces few and vague clinical signs during the first few weeks of life, when it is still possible to prevent irreparable brain damage. In the Finnish national screening programme for CHT, treatment is started at a median age of 6 days. According to multiple logistic regression analysis based on 102 cases, the main manifestations of CHT at this age are retardation of skeletal maturation and growth in length, icterus, large tongue, abdominal distension, skin mottling, muscle hypotonia and probably increased head size. The presence of other signs did not increase the probability of CHT. All signs are non-specific and some of the hypothyroid infants did not have any of them. Control of other confusing perinatal problems improved the diagnostic scoring but this did not increase the accuracy of prediction acceptably.

Psychomotor development in congenital hypothyroidism. The Greek screening programme

In 1979 a national screening programme for congenital hypothyroidism (CH) was introduced in Greece. Treatment with L-thyroxine was started immediately after confirmation of the diagnosis, at a median age of 28 days. A standardized development test (Griffiths) was given to a group of CH infants and to healthy controls at the ages of 5-7, 11-13, 17-19, and 23-25 months. Thirty-three infants with CH were also studied at the age of 35-37 months. The mean developmental quotient of CH infants was 103.8 +/- 12.0, 100.9 +/- 10.1, 103.3 +/- 7.1 and 99.8 +/- 10.2 from the ages of 5-7 to 23-25 months, and was not statistically different from those of the controls. Statistical analysis showed no significant differences between athyreotic children and those with an ectopic gland. Our findings show that the prognosis for psychomotor development of children with CH is quite good, provided that treatment starts in the first 6 weeks of life.

Psychomotor development of children with congenital hypothyroidism diagnosed by neonatal screening

The psychomotor development in 68 children with congenital hypothyroidism diagnosed during the first two years of a nationwide neonatal screening programme in Sweden was assessed during their first three years of life. Replacement therapy with thyroxine was initiated at the age of 15 +/- 7 days (mean +/- SD). Griffiths tests were performed in 15 patients at the age of 18 months and in 51 patients at 30-47 months. Their developmental quotients did not differ from those of control children, indicating that the psychomotor development in the children with congenital hypothyroidism was normal. In earlier studies of Swedish children with congenital hypothyroidism, diagnosed clinically before the age of three and a half years, the psychomotor development was found to be impaired. In contrast, the patients diagnosed by neonatal screening and given early therapy displayed normal results in Griffiths tests. This indicates that the age at the start of treatment is an important determinant for the prognosis.

Somatosensory evoked potentials and auditory brain-stem responses in congenital hypothyroidism. II. A cross-sectional study in childhood. Correlations with hormonal levels and developmental quotients

We report the results of somatosensory evoked potentials (SEPs) and auditory brain-stem responses (ABRs) done in 48 congenital hypothyroid (CH) treated children, early detected and aged 18 months, 3 and 5-9 years of age. We report also the results of SEP and ABR done in 9 3-year-old CH children, before and after a 1 month therapy interruption to reassess the thyroid status. The more frequent abnormalities were increased wave I latencies for 18 month and 3-year-old CH children. In some children, these increases were not associated with signs of otitis media. No significant difference was seen between CH children and controls for SEP latencies and ABR and SEP interpeak latencies (IPLs). Similarly, no significant difference was seen between the two recording sessions in the 9 3-year-old CH children for ABR and SEP. On an individual basis, we observed abnormalities of central conduction time for ABR and SEP in several CH children. Moreover, significant partial correlations were found between ABR and SEP IPLs and thyroxine (T4) serum levels at diagnosis and thyrotropin (TSH) serum levels at the time of recording. There was also a significant partial correlation between N19-P22 IPLs and the practical reasoning scale of the Griffiths test considering the whole group of CH children. These results indicate that SEP might eventually be used to detect CH children at risk of presenting developmental abnormalities.

Altered responsiveness to ambiental stimuli in altered thyroidal states

Hypothyroidal rats produced by low iodine diet or propylthiouracyl (PTU) were less active in the open field and received fewer food reinforcements than controls in a lever press situation at both 22 degrees C and 1 degree C. The hypothyroid rats also pressed less when heat was the reinforcer. On the other hand, hyperthyroidal rats produced by thyroid powder ingestion showed reduced emotionality in the open field. Acute exposure to cold failed to increase their alimentary or heat reinforced behavior. The results suggest that hypothyroidism produces a general inattention to the environment. This is found whether the environmental stimulus is an opportunity to explore, access to food or the availability of external heat.

Somatosensory evoked potentials and auditory brain-stem responses in congenital hypothyroidism. I. A longitudinal study before and after treatment in six infants detected in the neonatal period

We report the results of a longitudinal study of auditory brain-stem responses (ABRs) and somatosensory evoked potentials (SEPs) performed in 6 children with congenital hypothyroidism. These infants were detected by the Quebec Network for Genetic Medicine and treated early. ABRs and SEPs were recorded both before and 2 weeks after the initiation of therapy and at 6 months of age. Before treatment, for SEP, we found increased wave N19, P22 latencies and N13-N19, N19-P22 interpeak latencies (IPLs) in congenital hypothyroid (CH) children. For ABR, there were increased wave I latencies with normal I-V IPLs. Substitutive therapy improved these abnormalities although this improvement was more evident after a shorter period of time for ABRs than for SEPs. Even at 6 months, 2 CH children still showed increased N13-N19 IPLs. Both had very low serum T4 levels at the time of diagnosis and one had also a very small knee surface area, both criteria indicating a severe hypothyroidism. It will be interesting to verify if initial and persisting increase of N13-N19 IPL is associated with later neuropsychological problems.

Aspects of congenital hypothyroidism

This article describes aspects of congenital hypothyroidism, outlining retrospective studies and indicating the effects on development in childhood of the deficiency of thyroid hormone in early life. The intellectual problems persist into adult life and are associated with motor and behavioural abnormalities, causing social difficulties to many of the patients. Prospective screening and early treatment have resolved many of these difficulties but treatment must be given appropriately to ensure adequate progress.

Exploratory behavior, learning ability, and thyroid hormonal responses to stress in female rats rehabilitating from postnatal hypothyroidism

Newborn female Long-Evans rats were divided into groups of normal, hypothyroid [0.1% propylthiouracil (PTU) a reversible antithyroid goitrogen in the litter's drinking water], and hypothyroid rehabilitated (PTU water from birth to day 25, normal water thereafter). The rats were tested for several adaptive behavioral tasks between 40 and 90 days of age. At day 50, serum concentration of TSH and thyroid hormones revealed no detectable amounts of T4 and a 10-fold increase in TSH in the hypothyroid rats. At the same age in the rehabilitated animals, TSH levels were still below normal, a deficit fully normalized by day 90. Normal 50-day-old rats responded to pain stress (electric footshocks) by a significant depression of serum T4 and elevation of T3 levels within 10 min of treatment, whereas the rehabilitated animals exhibited an opposite pattern of response, i.e., an increase in the circulating T4 and a decrease in T3. At 50 days of age, both hypothyroid and rehabilitated rats showed decreased exploratory activity and no habituation in the hole-board test, whereas the locomotor activity of the rehabilitated females was significantly higher than that of the normals. No differences were found in the scores of passive avoidance learning (one trial step-through) among the three groups. Similarly, the rate of acquisition of the active one-way conditioned avoidance response (CAR) of the hypothyroid and rehabilitated rats did not differ significantly from that of the controls. However, the hypothyroid rats required significantly more unconditioned stimuli (footshocks) to acquire CAR and showed longer response latency and less intertrial responses. Although the hypothyroid rats showed no extinction of CAR, the rehabilitated rats were capable of extinction to an extent indistinguishable from normal rats. But compared with the normal animals, the rehabilitated rats showed significantly higher intertrial activity during both the acquisition and extinction phases of CAR.

Rehabilitation from neonatal hypothyroidism: spontaneous motor activity, exploratory behavior, avoidance learning and responses of pituitary--thyroid axis to stress in male rats

Long-Evans male rats were made hypothyroid from birth by the addition of 6-N-propylthiouracil (PTU) to their drinking water (0.1%). A group of animals was rehabilitated beginning at postnatal day 25 by withdrawal of the PTU from the drinking water. Subsequently, the rats were tested for a variety of behavioral tasks. Serum concentrations of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) were determined by radioimmunoassay. At 50 days of age, PTU-treated rats had non-detectable levels of T4 but an eight-fold increase of TSH. In 50-day-old, neonatally hypothyroid but rehabilitated rats, serum TSH and T3 were normal, although T4 was still significantly lower. At 90 days of age, basal levels of TSH and thyroid hormones were normal in the rehabilitated rats, but thyroid hormone secretion in response to various types of neural stress was markedly altered. Comparison of passive avoidance learning revealed no significant alteration in the memory retention of either PTU-treated or rehabilitated animals. The 50-day-old, rehabilitated rats showed increased locomotor activity both in running-wheel and in hole-board tests; this hyperactivity, though markedly reduced, still persisted at day 90. In the early phase of rehabilitation (50 days of age), decreases in exploratory activity and lack of habituation occurred with the hole-board test; by the late phase of rehabilitation (90 days of age) these behavioral parameters had become normal. These results suggest generally longer periods of plasticity of the brain and better prospects for rehabilitation from neonatal cretinoid retardation than commonly believed. Specifically, the pituitary-thyroid system and neural mechanisms integrating adaptive behavior possess considerable capacity for spontaneous recovery from hypothyroidism; certain types of altered neuroendocrine and behavioral responses appear to be less amenable to rehabilitation or require longer periods for complete rehabilitation.

Permanent defects in rat peripheral auditory function following perinatal hypothyroidism: determination of a critical period

Rats were treated with propylthiouracil (PTU) for 10-day periods beginning at different ages. Daily injections of L-thyroxine (T4) were administered concurrently with PTU to a group of rats which served as one control group. Peripheral auditory function was evaluated by the brainstem response audiometry (BSRA) technique performed at 12, 16, 25 and 120 days of age. PTU treatment significantly increased wave I latency (cochlear nerve compound action potential) in adult rats when administered from 3 days before delivery through 6 days of age, but was without permanent effect (wave I latencies and thresholds) when administered for 10 days starting at 10 days after birth. T4 replacement during the first 10 postnatal days prevented permanent abnormalities. These data suggest that the period of greatest vulnerability to thyroid hormone depletion in the peripheral auditory system extends from at least 3 days before delivery through between 5 and 10 days of age.

Finnish national screening for hypothyroidism. Few false positives, early therapy

National cord blood screening for congenital hypothyroidism has operated in Finland with complete coverage since 1980. A low frequency of false positives, 0.08%, was achieved by supplementing the TSH screen with a T4 determination in borderline samples. Among 175188 infants the incidence of (unconfirmed) hypothyroidism was 1/2637. The median age at start of therapy was 6 days. The programme imposed a 2-3 week therapy on the false positive cases. This did not appear to cause any adverse effects. A mechanism for masking congenital hypothyroidism was observed: two athyroid infants were euthyroid at birth because of feto-fetal transfusion.

The development of children with congenital hypothyroidism

Standardised motor, intellectual and behavioural tests were undertaken in a group of 56 children in the north of England. All were aged between five years and 15 years 11 months and all had congenital hypothyroidism. The results were compared with those of a control group. The mean IQ of the hypothyroid group was found to be 1 to 2 standard deviations below the population mean. In the group there was no correlation between developmental measures and age at diagnosis but in a subgroup with bone-age evidence of prenatal hypothyroidism there was a correlation between age at diagnosis and both intellectual and motor development. Intellectual development was normal among those treated before one month of age, but there was some evidence of disturbed fine motor and cerebellar functions.

Serum alpha-fetoprotein--a biochemical indicator of prenatal hypothyroidism

Serum alpha-fetoprotein (AFP) was analysed at 10-30 days of age in infants with positive TSH screening tests for congenital hypothyroidism. These levels were significantly higher in infants with true positive screening tests than in those with false positive tests; 27 of 43 infants with congenital hypothyroidism had serum AFP levels above the age-related reference range. The postnatal rate of elimination of AFP from serum did not differ in hypothyroid and euthyroid infants, indicating that the difference in serum AFP was due to more extensive synthesis in hypothyroid individuals. The level of serum AFP was inversely correlated with the roentgenological skeletal maturation index. It is postulated that increased serum AFP is caused by prenatal hypothyroidism and that analysis of serum AFP is a valuable tool to identify those infants with congenital hypothyroidism who are at risk of neuropsychological sequelae.

Congenital hypothyroidism and changes in the enamel of deciduous teeth

Deciduous teeth from children with congenital hypothyroidism were collected and ground sections were prepared. The sections were analysed by means of polarized light and microradiography. The enamel in ground sections of deciduous teeth from children with congenital hypothyroidism showed an increase in areas with elevated pore volume distribution in both the pre- and postnatal enamel. The findings suggest that thyroid hormone influences enamel maturation. Further, alterations in enamel structure, presumably due to prenatal thyroid deficiency, were found to be more common among children with neurological abnormalities at the age of 7 to 9 years.

Congenital hypothyroidism in Sweden. Psychomotor development in patients detected by clinical signs and symptoms

Thirty-nine children at 7 to 9 years of age with congenital hypothyroidism have been studied with respect to their intellectual, neurological and social functions. Their intellectual achievement as assessed by the WISC test, was significantly lower than in a reference population (mean IQ 88, range 50-113). In children who showed signs and symptoms of hypothyroidism during their first four weeks of life, there was a negative correlation between the age when therapy was started and intellectual development. No such correlation was found in children who showed signs and symptoms after the first four weeks of life. Nine children of 26 with signs of hypothyroidism in the neonatal period, were found to have neurological abnormalities consisting of fine and gross motor disturbances. The neurological abnormalities seriously affected daily life in only the two most severely mentally retarded. No correlation was found between the age when the therapy was started and neurological abnormalities. Three children attended special schools because of mental retardation and six attended normal schools but required additional teaching assistance for learning disabilities. Our results suggest that the risk of future intellectual handicaps may be reduced by early treatment in children with hypothyroidism presenting during the neonatal period.

Screening for congenital hypothyroidism. II. Clinical findings in infants with positive screening tests

In a pilot screening programme for congenital hypothyroidism, PKU filter paper blood samples from 20 000 infants born in Stockholm were analysed for TSH and T4 to identify optimal conditions for routine nationwide screening. Among 160 infants with positive screening tests, 7 infants (group I) had true-positive results, 6 had primary and one secondary hypothyroidism. The 153 infants with false-positive tests were divided into group II:74 infants with an isolated increased TSH level; group III: 71 infants with an isolated decreased T4 concentration; and group IV: 8 infants with increased TSH and decreased T4 levels. In group I the clinical signs and symptoms of hypothyroidism varied when the diagnosis was made at 3 weeks of age. The median hypothyroid index score was 8 (range 0--18). In groups II-IV most infants showed very few signs of hypothyroidism. The median hypothyroid index scores were 1, 1, and 0, respectively. Clinical findings were of little value in the individual case for distinguishing true from false positive screening tests. We suggest that nation-wide screening should be based on TSH analyses of PKU blood samples, with a cut-off level corresponding to 50 mU/l of plasma. Recall frequency will be less than 0.1%.

Screening for congenital hypothyroidism in the Republic of Ireland

A national pilot study for detecting congenital hypothyroidism by radioimmunoassay of thyroid-stimulating hormone concentrations in dried blood was incorporated into the newborn screening programme in Ireland on 1 August 1979. The programme has been monitored by a steering committee and follows the guidelines set by the European Society of Paediatric Endocrinologists. During the first 12 months 76 224 infants were screened and 19 cases confirmed, giving an incidence of 1:4012. Fifty infants (0.07%) were recalled for a serum sample, though most of the recalls (31; 0.04%) occurred during the first three months, before the methodology had become established. No case was detected clinically. At recall only three of the 19 affected infants had obvious features, and nine inconspicuous features. Organisation was directed at early diagnosis and treatment, the mean age at beginning treatment being 15 days. These results confirm the efficacy of screening for congenital hypothyroidism and suggest that capital and running costs will be offset by savings in maintenance treatment of untreated patients. Screening does not, however, remove the need for continued vigilance, and clinicians should request thyroid-function tests in any suspected case.