[Histofunctional state of the thyroid gland in pregnancy and in progeny under experimental regime of iodine intake]

The paper is devoted to the study of the character of structural changes in the thyroid gland in pregnancy and in progeny of rats with deficient or excessive intake of iodine. A stable model of thyroid transformation was developed under the conditions of the changed regimen of iodine intake in pregnancy. Predominantly proliferative changes of the epithelial component in the thyroid tissue developed in pregnancy both with deficient and excessive iodine. Based on the histochemical, morphometric, histostereometric analysis a close relationship between the character of transformation of maternal thyroid and the progeny thyroid tissue was found. Dynamics of the development of postnatal thyroid tissue in the presence of congenital structural-functional disorders is described.

Mutations in the gene encoding thyroid transcription factor-1 (TTF-1) are not a frequent cause of congenital hypothyroidism (CH) with thyroid dysgenesis

Permanent congenital hypothyroidism (CH) has an incidence of 1/3000-4000 newborns and is among the most frequent cause of mental retardation and neurological alterations in children. In 80% to 85% of cases CH is associated with thyroid dysgenesis. A group of 61 patients with CH (22 with agenesis, 18 with ectopy, 1 with hypoplasia, and 20 cases with CH without thyroid enlargement but not further characterized) and 30 normal subjects were examined for the presence of mutations in the gene encoding the thyroid transcription factor 1 (TTF-1). The coding-region of the TTF-1 gene was analyzed in all cases by the single stranded conformational polymorphism (SSCP) and no mutations were detected. Direct sequencing also carried out in patients with thyroid agenesis confirmed the absence of mutations or polymorphisms in the TTF-1 gene. The absence of mutations in the TTF-1 gene in our samples indicates that the mutations in the TTF-1 gene are not a frequent cause of CH.

Absence of mutations in the gene encoding thyroid transcription factor-1 (TTF-1) in patients with thyroid dysgenesis

Thyroid transription factor-1 (TTF-1) is a homeodomain-containing nuclear transcription factor, important in regulation of the thyroid-specific genes thyroglobulin (Tg), thyroperoxidase (TPO), and thyrotropin receptor (TSHR). TTF-1 is an early biochemical marker of thyroid differentiation, essential for thyroid development and maintenance of the thyroid differentiated state. It is possible that mutations in titf1 gene encoding TTF-1 could result in failure of the thyroid gland to develop. Single strand conformation polymorphism (SSCP) was used to detect the presence of titf1 gene mutation in a group of 15 patients with congenital hypothyroidism. The etiology of the congenital hypothyroidism included thyroid agenesis (9), sublingual ectopic thyroid (4), and severe hypoplasia (2). The analysis did not identify any titf1 gene mutation, among these patients. These results rule out the presence of titf1 mutations, at least in the coding region, in our thyroid dysgenesis patients. Mutations in titf1 coding region may be an extremely rare event, and was not detected in our small sample size or, alternatively, such a mutant might even be viable since TTF-1 plays an important role in lung, brain, and pituitary development.

Thyroid hemiagenesis with subacute thyroiditis

A 58-year-old woman with thyroid hemiagenesis associated with subacute thyroiditis is described. Physical examinations revealed a firm nodule with spontaneous pain and tenderness in the left thyroid lobe. A serum thyroid hormone levels were elevated and thyroid scintiscan with 99mTc pertechnetate showed an extremely low uptake, we made a diagnosis of subacute thyroiditis. A 201Tl thyroid scan demonstrated an enlarged left lobe and absence of the right lobe. Ultrasonography of the thyroid gland revealed an enlarged left lobe occupied mostly with a hypoechoic region. An incidental finding was absence of the right lobe. Two months later thyroid function returned to normal. A follow-up thyroid scintiscan revealed a normal left lobe but absent right lobe. The diagnosis of hemiagenesis was confirmed by CT scan. This appears to be the first case report of thyroid hemiagenesis associated with subacute thyroiditis.

Review of antithyroid drug use during pregnancy and report of a case of aplasia cutis

Thioamide therapy has improved the outcome of pregnancies complicated by maternal hyperthyroidism, without long-term effects on cognitive and somatic development. However, there remain questions concerning whether these drugs, especially methimazole (MMI), may be associated with aplasia cutis congenita (ACC) and how best to avoid impairment of fetal thyroid function during their use. We report an example of ACC and review the relevant literature. We conclude that there is insufficient evidence either to establish or eliminate a direct causal relationship between ACC and MMI use. Since propylthiouracil is an equally effective antithyroid agent and has not been associated with ACC, it is the preferred thioamide for hyperthyroidism during pregnancy. Our review also indicates that impairment of neonatal thyroid function may be minimized by using a thioamide dose that is just sufficient to maintain the maternal serum free thyroxine concentration in the high normal or slightly thyrotoxic range.

[The role of ultrasonography in thyroid disease]

Ultrasound examination of the thyroid gland is widely used in the diagnosis of thyroid disease. This test is easy and rapid to perform, widely available and the results are readily interpreted. Using ultrasound the image of foci of disease within the gland are easily identified, especially using high frequency probes which enable solid nodules up to approx 3 mm to be revealed with 10 MHz probes. In non-nodular thyroid disease the ultrasonic structure guides the diagnosis (thyroiditis, Graves' disease). During the follow-up of thyroidectomised patients ultrasound can easily reveal postoperative anatomic variations and an early diagnosis can be obtained of any signs of local recurrence of the primary disease. Only hemiagenesia and hypoplasia can be accurately evaluated in congenital disease, whereas in the event of the persistence of the thyroglossal duct the latter can only be diagnosed if it presents a cystic evolution. Thyroid ectopia cannot be identified and must be studied using thyroscintigraphy, preferably performed using 131I as the isotope. The acquired pathology is classified into phlogistic processes, diffuse or nodular hyperplasia, benign and malignant neoplasia. This classification is widely accepted by virtually all authors. In thyroiditis, ultrasound may facilitate the diagnosis of De Quervain's non-suppurative sub-acute thyroiditis (TANS) and Hashimoto's chronic thyroiditis, although always in association with clinical and laboratory tests. The most frequent thyroid pathology is without doubt goitre. This disorder may occur in a non-nodular (widespread goitre with an endemic or sporadic pattern) or nodular form which may be single or multiple. The term goitre is used to indicate the increased volume of the thyroid gland independently of the causes which have provoked it. Common goitre is defined as being endemic when in some geographic area 10% of the general population or 20% of the school-aged population suffers from thyroid hyperplasia (areas of goitrogenic endemic disease). Graves' disease may be included in the group of thyroid hyperplasia diseases, although it is distinguished from the simple versions by the marked glandular hyperactivity which creates manifest hyperthyroidism. In this pathology ultrasonography must be supplemented by colour-Doppler wherever possible. Thyroid nodules are subdivided in terms of their echostructure into 5 types: liquid, mixed (prevalently solid or prevalently liquid), hyperechogenic solid, isoechogenic solid and hypoechogenic solid. The characteristics of benign nodules are: hypoechogenic structure, regular edges, complete and uniform hypoechogenic peripheral halo.(ABSTRACT TRUNCATED AT 400 WORDS)

Has percutaneous umbilical blood sampling improved the outcome of high-risk pregnancies?

PUBS offers distinct advantages to the perinatologist in the management of the high-risk pregnancy. Improvement in outcome has clearly been attained in the severely anemic fetus, for example, whereas fetal blood sampling has also led to great advances in both diagnosis and treatment of many other perinatal abnormalities. The exact role for PUBS in the management of problems such as intrauterine growth retardation and the fetus at risk for thrombocytopenia in ITP remains controversial. It is quite evident, however, that overall PUBS offers tremendous aid to the perinatologist in management of the high-risk pregnancy, with future promise for even greater application.

Spectrum of serum thyroglobulin elevation in congenital thyroid disorders

Serum thyroglobulin (Tg) data are presented for 47 infants with congenital thyroid disorders. Abnormal elevation of serum Tg (> 250 micrograms/L) occurred in 17% of the population studied, whereas values in excess of 1,000 micrograms/L were demonstrated in 11% of infants. The latter group includes the first report of supraphysiologic Tg elevation in an infant with thyroid gland ectopia, and the highest reported thyroglobulin level in the syndrome of generalized thyroid hormone resistance in an infant homozygous for a novel deletion in the c-erbA beta receptor. Mechanisms involved in the pathogenesis of Tg elevation are discussed. We conclude that Tg elevation in congenital thyroid disorders is more common than previously recognized, and values > 1,000 micrograms/L identify infants with a spectrum of anatomic and biochemical abnormalities.

Risk factors for developmental disorders in infants born to women with Graves disease

OBJECTIVE

To identify risk factors for disorders of fetal growth and thyroid function in the presence of maternal Graves disease.

METHODS

Two hundred thirty pregnancies in gravidas with Graves disease were analyzed. Maternal thyroid status was evaluated by serum free thyroxine (T4) or free T4 index, TSH, and TSH-receptor antibody; personal history of thyrotoxicosis and total dose of antithyroid drugs during pregnancy were also noted. Neonatal thyroid function was assessed at birth and on the fifth day after birth.

RESULTS

Fifteen neonates (6.5%) were small for gestational age (SGA), and this occurrence was significantly associated with thyrotoxicosis lasting for 30 weeks or more of pregnancy, TSH-receptor antibody level of 30% or more at delivery, history of Graves disease of 10 years or longer, and onset of Graves disease before 20 years of age. However, no significant correlation was found between maternal thyroid hormone level and SGA neonates. Thyroid dysfunction developed in 38 infants (16.5%), of whom only four were SGA; development of this dysfunction was significantly related to the mother's total dose of antithyroid drugs, duration of thyrotoxicosis in pregnancy, and/or TSH-receptor antibody level at delivery.

CONCLUSIONS

Duration of maternal Graves disease or thyrotoxicosis, either mild chemical or overt, in pregnancy is significantly associated with SGA neonates. Neonatal thyroid dysfunction is associated with the maternal thyroid condition, especially the serum TSH-receptor antibody level.

Acute suppurative thyroiditis with bilateral piriform sinus fistulae

Although there are many possible routes of infection in AST, the clinician must be aware of a possible fistula between the piriform sinus and the perithyroidal space--especially in patients with recurrent episodes of AST. Diagnosis of this congenital tract requires a high index of suspicion and radiographic demonstration by a barium swallow or endoscopic visualization. Effective treatment of AST with intravenous antibiotics and appropriate surgical intervention have greatly reduced the mortality and secondary complications. Complete fistulectomy, however, is required for permanent cure.

Congenital pyriform sinus fistula: a cause of acute left-sided suppurative thyroiditis and neck abscess in children

Acute bacterial thyroiditis or neck abscesses in children can be caused by infection through pyriform sinus fistulae which usually originate from the tip of the left pyriform sinus. They are thought to be remnants of either the third or fourth pharyngeal pouches. CT, ultrasound and gastrointestinal contrast studies are all useful in clarifying the pathological process and showing the extent.

Lingual thyroid in two natural brothers

Tc99m scanning because of hypothyroidism revealed a lingual thyroid in two natural brothers who had no family history of thyroid disease. No thyroid tissue was found in the neck. Further development under substitution therapy with levothyroxine was normal. The diagnosis of this rare disease in two natural brothers suggests that lingual thyroid may be inherited.

[Children of hyper- and hypothyroid mothers]

A multicenter study was able to utilize 120 medical files of children born from mothers who presented an abnormal thyroid function, 67 euthyroid goiters, 29 hyperthyroidisms, and 24 hypothyroidisms. In the first case, whether or not an inhibiting treatment was initiated, all children were perfectly normal. In case of maternal hyperthyroidism, the risk of malformations is not increased, deaths in utero and mostly in utero growth delays (1 case in 2) are more frequent. At birth, the child may present a hyperthyroidism due to the effect of SAT with elevated TSH and a goiter, sometimes compressing and impairing breathing, or also a hyperthyroidism due to transplacental crossing of stimulating immunoglobulins with possibility of thyreotoxic crises and heart failure. The diagnosis could be made in utero in the presence of tachycardia or with T4 and TSH assays in the cord. In case of maternal hypothyroidism, usually the children have no problems and the risk of neonatal hypothyroidism is mostly present in premature infants if the maternal balance is poor (2 in 24 cases in our series). Finally, in the reference population, the risk of neonatal hypothyroidism remains 1 in 3600 and justifies systematic screening on the 5th day of life.

Profile of thyroid disorders in a referral centre in north India

From 1983-88, 157 patients were investigated in our clinic for thyroid disorders: 117 (75%) were hypothyroid, 10 (6%)-hyperthyroid, and 30 had euthyroid goiters. Average age of presentation of congenital hypothyroids was 4.07 years. Children with goitrous hypothyroidism (n = 19) were divided into: (i) thyroiditis: RAIU low and patchy, TMA positive: 2 children; (ii) dyshormonogenesis: RAIU high, family history positive, perchlorate discharge test positive: 2 children; (iii) iodine deficiency: RAIU high, urinary iodine low: 2 children, and (iv) cause unknown: RAIU normal or high, other investigations normal: 13 children. Ninety eight hypothyroid children without goiter were divided into 6 groups: (i) athyreosis: RAIU low, no thyroid tissue identifiable (n = 39); (ii) hypoplasia: RAIU low, gland small, in normal position (n = 7); (iii) ectopia: RAIU low, gland in ectopic position (n = 24); (iv) thyroiditis: TMA positive (n = 2); (v) iodine deficiency: low urinary iodine (n = 1); and (vi) cause unknown: RAIU and scan normal, other investigations normal and not done (n = 8). Proportionate short stature was present in 44.4% children. Twenty two children presented only with growth failure; 72% of them had dysgenetic glands. Early onset marked the group with hyperthyroidism (n = 10). Euthyroid goiter was present in 30 (19%). Hypothyroidism is still being diagnosed very late. All children with growth failure, even if proportionate, must have thyroid status evaluated.

[Congenital piriformo-thyroid fistula as a cause of recurrent suppurative thyroiditis]

A previously healthy five year old boy presented with suppurative, febrile thyroiditis of the left lobe with pronounced general and local signs of inflammation, normal thyroid function and lack of thyroid antibodies. Intravenous antibiotic therapy improved the condition quickly. Six and nine months later however recurrent left lobe thyroiditis occurred. Endoscopic examination showed an internal fistula from the left piriform sinus to the left thyroidal lobe which was cut out. The case report confirms previous communications, that recurrent suppurative thyroiditis is nearly always caused by a piriform sinus fistula, probably a fourth pharyngeal pouch remnant which can be cured surgically.

Prescribing in pregnancy. Thyroid disease

When treating thyroid disease, as with other conditions in pregnancy, one is concerned with the welfare of both mother and developing child. Thyroid disease causes few maternal problems; thyrotoxicosis in fact tends to improve in pregnancy, allowing medical management with lower drug doses than usual. Relapse of thyroid disease may occur postpartum, when transient hypo- and hyperthyroidism are relatively common. In contrast, the fetus and neonate are threatened in a number of ways by drugs given to the mother and by transplacental passage of maternal antibodies capable of inducing thyroid disease. Antithyroid drugs may cause fetal goitre with airway obstruction, and are associated with mild neonatal hypothyroidism. Thyroid antibodies in primary myxoedema and Hashimoto's thyroiditis are occasionally implicated in neonatal hypothyroidism and may even cause thyroid dysgenesis. Neonatal hyperthyroidism has a high morbidity and mortality and may have long-term skeletal effects such as craniosynostosis. Fetal problems may not be apparent at birth but may emerge in the next eight to ten days, especially in hyperthyroidism when the mother has been on treatment. Close monitoring throughout pregnancy and for the first ten days postpartum is required to minimize risks to the fetus and neonate. Most pregnancies associated with thyroid disease will have a successful outcome. If the occasional at-risk fetus is to be identified and treated successfully there should ideally be close cooperation between obstetrician, endocrinologist and paediatrician.

Free triiodothyronine and free thyroxin in sera of pregnant women and subjects with congenitally increased or decreased thyroxin-binding globulin

Concentrations of free thyroxin (T4) and free triiodothyronine (T3) were measured in sera from pregnant women, in subjects with congenitally increased or decreased thyroxin-binding globulin (TBG), and in euthyroid controls. Measured free hormone concentrations were compared with calculated values for free hormone derived from concentrations of total T4, total T3, and binding proteins. Measured and calculated concentrations of free T4 and free T3 were below normal in the pregnant subjects but were normal in subjects with congenital increases of TBG. The low concentrations of free hormone in pregnancy are at variance with the euthyroid status of these subjects. Measured free T4 was normal, but concentrations of free T3 were less in the euthyroid congenitally low-TBG group.

Advancing in tandem: clinical endocrinology and clinical chemistry

Here I review some of the recent accomplishments in clinical endocrinology and clinical chemistry, point out the direction of future work, and try to predict some of the advances of the next decade. Endocrinology, perhaps more than any other branch of clinical medicine, is rooted in biochemistry and physiology. Endocrinologists have been leaders in the development of methods, which have been adapted by clinical chemists for wider applications than those conceived originally. For the sake of brevity, I shall not recount the early history of endocrinology in this century--or the enormous progress since Starling coined the term "hormone" and stated the physiological role of these chemical messengers in 1905. Progress in endocrinology in recent years has been astounding.

Peripheral resistance to thyroid hormone in an infant

Peripheral resistance to thyroid hormone, a syndrome characterized by elevated serum total and free thyroid hormone levels and abnormal TSH suppression without manifestations of hyperthyroidism, was studied in a clinically euthyroid 6-month-old infant. Initial serum concentrations of T4, T3, and TSH were 22.1 micrograms/dl, 334 ng/dl, and 7.6 microunits/ml, respectively; infusion of synthetic TRH increased the serum TSH to 47.4 microunits/ml, an exaggerated response. Pituitary insensitivity to T3 was investigated by measuring these parameters in response to consecutive 7-day courses of increasing doses of T3. Four times the calculated replacement dose of T3 (40 micrograms/day) was required to normalize the serum T4 and the serum TSH response to TRH. After administration of 80 micrograms/day T3, the serum TSH response to TRH was virtually abolished, but no clinical signs of thyroid hormone excess were observed. High doses of T4 blunted the serum TSH response to TRH in a manner similar to T3. Prednisone also decreased the TSH response to TRH but had no effect on serum thyroid hormone concentrations. In an attempt to determine the mechanism of thyroid hormone resistance, specific nuclear T3 binding was compared in cultured skin fibroblasts from the patient and a normal infant. Normal fibroblast nuclei had a single binding site with a Ka of 3.1 X 10(9) M-1. In contrast, the Scatchard plot of the patient's T3 binding was curvilinear, compatible with a high affinity site that had a Ka (4.2 X 10(9) M-1) similar to that of the normal fibroblasts and a second low affinity site (Ka = 2.7 X 10(8) M-1). Supraphysiological concentrations of T3 elicited a dose-related increase in fibroblast glucose consumption, which was similar in cells from both the patient and from a normal infant. In conclusion, pituitary and peripheral resistance to thyroid hormone has been demonstrated in this infant, but despite the abnormality of nuclear T3 binding, the cellular mechanisms remain unclear.

[Peroxidase and human thyroid hormone synthesis disorders (author's transl)]

Thyroid peroxidase in involved in several steps of the biosynthesis of thyroid hormone utilizing H2O2: peroxidation of iodide to iodine, iodination of thyroglobulin (Tg) and coupling reaction leading to T4 and T3 formation. The peroxidase enzyme appears to be an heme protein containing a protoporphyrin IX, with binding sites for both iodide and tyrosine. Although the peroxidase is present in numerous cellular structure, iodination activity occurs primarily if not only at all, at the apical cell border. Lack of peroxidase activity or abnormal peroxidase has been described in isolated cases of congenital goiter with organification defect and a positive perchlorate test. However no change in enzymatic activity has been found in patients with Pendred's syndrome as compared to normal tissue. The deficiency of hormone synthesis observed in various benign diffuse thyroid disorders in certainly not due to a lack of peroxidase activity. In treated hyperthyroid patients, a high cellular activity is observed, especially at the apical cell border. In euthyroid patients with diffuse sporadic goiter, an increase of peroxidase activity is also observed. However, the cytochemical localization of the enzyme in goitrous thyroid gland shows that the peroxidase activity is mostly visualized around numerous lipoid structures; being concentrated in this particular site, the enzyme might preferentially oxidize lipids and consequently be less available for hormone synthesis. In euthyroid hot nodule, the peroxidase activity is normal. In cold nodule, a discrepancy between iodide oxidation and protein iodination has been found, suggesting that iodide peroxidation and iodination of tyrosine residues of Tg are two relatively independent processes although thyroid peroxidase catalyses both reactions. In contrast with the benign pathological conditions, the peroxidase activity is lower than normal in thyroid cancerous tissue.