Permanent vs Transient Congenital Hypothyroidism: Assessment of Predictive Variables

OBJECTIVE

To assess clinical variables, including early thyroid scintigraphy, in predicting the outcome (permanent vs transient) in term infants with congenital hypothyroidism (CH).

METHODS

In a retrospective study, 142 full-term infants with CH diagnosed between 2000 and 2012 were categorized into three groups: agenesis/ectopic thyroid and permanent CH; eutopic thyroid and permanent CH; and eutopic thyroid and transient CH. All underwent early thyroid scintigraphy and were under regular follow-up in our tertiary Pediatric Endocrine Institute.

RESULTS

Thyroid scan showed agenesis/ectopic thyroid in 58 (41%) and eutopic thyroid in 84 (59%) infants. Imaging findings were similar in eutopic-permanent and eutopic-transient groups. At initial evaluation, TSH levels were higher in the agenesis/ectopic group than in the eutopic-permanent and eutopic-transient groups (71.5 ± 11.2 mIU/L vs 49.1 ± 27.9 mIU/L and 42.5 ± 29.1 mIU/L, respectively; P < 0.001). Higher l-T4 doses were required from the third month in the agenesis/ectopic than in the eutopic-permanent group (P < 0.001) and from the sixth month in the eutopic-permanent than in the eutopic-transient group (P < 0.01). Initial TSH >63.5 mU/L (P < 0.001) and l-T4 dose >4.6 μg/kg/d at age >6 months (P < 0.001) were found to be predictors for an agenesis/ectopic gland using receiver operating characteristic analysis, as was an l-T4 dose >2.2 μg/kg/d at age >6 months (P < 0.01) for permanent CH in patients with a eutopic gland.

CONCLUSIONS

Although early thyroid scintigraphy is reliable in predicting permanent CH when detecting agenesis or ectopic gland, it cannot differentiate between permanent and transient CH in cases with a eutopic thyroid. Confirmatory TSH at diagnosis and the l-T4 dose through treatment may better distinguish between permanent and transient CH.

Thyroid Hemiagenesis: Incidence, Clinical Significance, and Genetic Background

CONTEXT

Thyroid hemiagenesis (THA) constitutes a rare, congenital disorder that is characterized by an absence of one thyroid lobe. Because the pathogenesis and clinical significance of this malformation remain undefined, specific clinical recommendations are lacking, especially for asymptomatic cases.

EVIDENCE ACQUISITION

The PubMed database was searched (years 1970 to 2017), and the following terms were used to retrieve the results: "thyroid hemiagenesis," "thyroid hemiaplasia," "one thyroid lobe agenesis," and "one thyroid lobe aplasia." Subsequently, reference sections of the retrieved articles were searched.

EVIDENCE SYNTHESIS

There is a noticeable susceptibility of subjects with THA to develop additional thyroid and nonthyroidal pathologies. In pathogenesis of concomitant thyroid pathologies, a chronic elevation in thyroid-stimulating hormone values may play an important role. Thus far, genetic studies failed to find a common genetic background of the anomaly, and the potential underlying cause was identified in a minority of the cases.

CONCLUSIONS

Patients with THA are prone to develop additional thyroid pathologies and theoretically might benefit from l-thyroxine treatment to lower the thyrotropin levels to those observed in the normal population. However, further research should be done to ascertain whether such intervention early in life would prevent development of associated thyroid conditions. At least, increased vigilance should be maintained to reveal all of the concomitant disorders as soon as possible during follow-up examinations. Application of high-throughput technologies enabling a genome-wide search for novel factors involved in thyroid embryogenesis might be the next step to expand the knowledge on THA pathogenesis.

Seasonal variations in TSH serum levels in athyreotic patients under L-thyroxine replacement monotherapy

BACKGROUND

Whether serum TSH undergoes seasonal fluctuations in euthyroid and hypothyroid residents of temperate climates is controversial.

METHODS

Monthly TSH and thyroid hormone levels were cross-sectionally analysed in a large cohort of euthyroid subjects (n=11 806) and L-thyroxine (L-T4)-treated athyreotic patients (n=3 934). Moreover, in a small group (n=119) of athyreotic patients treated with an unchanged dosage of L-T4 monotherapy, hormones were measured both in the coldest and in the hottest seasons of the same year (longitudinal study).

RESULTS

No seasonal hormone change was observed in the euthyroid subjects except for a small FT3 increase in winter (+2.9%, P<.001). In contrast, the L-T4-treated athyreotic patients had significantly higher serum TSH values in the cold season when the FT4 values were significantly lower. The differences were more notable in the longitudinal series (TSH, 0.80 vs. 0.20 mU/L and FT4, 16.3 vs. 17.8 pmol/L in December-March vs. June-September, respectively). In these patients also serum FT3 values significantly decreased in winter (in the longitudinal series, 3.80 in winter vs 4.07 pmol/L in summer). Regression analysis showed that in athyreotic subjects, a greater FT4 change is required to obtain a TSH change similar to that of euthyroid controls and that this effect is more pronounced in the summer.

CONCLUSION

Athyreotic patients undergoing L-T4 monotherapy have abnormal seasonal variations in TSH. These changes are secondary to the FT4 and FT3 serum decreases in winter, which occur in spite of the constant treatment. The underlying mechanisms are unclear, but in some cases, these changes may be clinically relevant.

The different requirement of L-T4 therapy in congenital athyreosis compared with adult-acquired hypothyroidism suggests a persisting thyroid hormone resistance at the hypothalamic-pituitary level

BACKGROUND

Levothyroxine (l-T4) is commonly employed to correct hormone deficiency in children with congenital hypothyroidism (CH) and in adult patients with iatrogenic hypothyroidism.

OBJECTIVE

To compare the daily weight-based dosage of the replacement therapy with l-T4 in athyreotic adult patients affected by CH and adult patients with thyroid nodular or cancer diseases treated by total thyroidectomy.

DESIGN AND METHODS

A total of 36 adult patients (27 females and nine males) aged 18-29 years were studied; 13 patients (age: 21.5±2.1, group CH) had athyreotic CH treated with l-T4 since the first days of life. The remaining 23 patients (age: 24±2.7, group AH) had hypothyroidism after total thyroidectomy (14 patients previously affected by nodular disease and nine by thyroid carcinoma with clinical and biochemical remission). Patient weight, serum free thyroid hormones, TSH, thyroglobulin (Tg), anti-Tg, and anti-thyroperoxidase antibodies were measured. Required l-T4 dosage was evaluated. At the time of the observations, all patients presented free thyroid hormones within the normal range and TSH between 0.8 and 2 μIU/ml.

RESULTS

Patients had undetectable Tg and anti-thyroid antibodies. The daily weight-based dosage of the replacement therapy with l-T4 to reach euthyroidism in patients of group CH was significantly higher than that in those of group AH (2.16±0.36 vs 1.73±0.24 μg/kg, P<0.005). Patients of group CH treated with l-T4 had significantly higher serum TSH levels than patients of group AH (P=0.05) as well as higher FT4 concentrations.

CONCLUSIONS

To correct hypothyroidism, patients of group CH required a daily l-T4 dose/kg higher than group AH patients, despite higher levels of TSH. The different requirement of replacement therapy between adult patients with congenital and those with surgical athyroidism could be explained by a lack of thyroid hormones since fetal life in CH, which could determine a different set point of the hypothalamus-pituitary-thyroid axis.

Unexpected conversion from hypothyroidism to an euthyroid state due to Graves' disease in a patient with an ectopic thyroid

A 15-year-old woman was diagnosed with hypothyroidism and unilateral ectopic thyroid. Levothyroxine treatment was introduced; however, the patient was non-compliant and took the medication irregularly. When she presented to an endocrinologist at the age of 30, she had not been using levothyroxine for at least 6 months. Surprisingly, she was clinically and biochemically euthyroid. Due to decreased echogenicity on ultrasound examination, enhanced vascularization on Color Doppler examination and increased concentration of anti-TSH receptor autoantibodies, she was diagnosed with Graves' disease. Eventually, she underwent total thyroidectomy due to diagnosis of follicular neoplasm in fine-needle aspiration biopsy of the focal lesion found in the thyroid gland. To our knowledge, our patient is the first described with ectopic thyroid, presenting a nodular variant of Graves' disease and no signs of orbitopathy, who was initially hypothyroid and became euthyroid in the course of autoimmune thyroid disease.

Infant's bilobar thyroid agenesis and mother's I-131 accidental administration

Bilobar thyroid agenesis is one of rare diseases. Genetic and environmental factors may associate with bilobar thyroid agenesis. But the mechanism is still not completely understood. It had been showed that I-131 administration during pregnancy may induce thyroid dysfunction in newborn. Here we reported a case of female hospital staff who received I-131 accidently during (10-12th gestational weeks) and after her pregnancy. The absorbed dose to fetus was higher than 30mGy. At birth, the infant was found to have no thyroid. It was speculated that the fetal thyroid agenesis may be related with mother' I-131 administration during pregnancy. In addition, this case report also indicated that the radiation dose should be minimized to any developing embryo.

[Congenital hypothyroidism secondary to thyroid hypoplasia detected in adulthood]

The anatomical location of the thyroid gland and its hormone byosinthesis are regulated by the expression of certain genes, whose disruption leads to the so-called thyroid dysgenesis: agenesis, ectopia and hypoplasia, and to dyshormonogenesis. We present the case of a patient with mental retardation and hypothyroidism whose diagnosis was made in adulthood. Biochemical determinations confirmed the diagnosis without evidence of thyroid autoimmunity. This patient represents the extended evolution of a thyroid hypofunction, which lasted in an unsuspected way for 53 years, with important consequences of this deficiency at diagnosis. Exogenous therapy achieved great improvement in clinical symptoms, but did not reverse the neurological damage attributable to the lack of thyroid hormone necessary for fetal development. The necropsy revealed little thyroid tissue in the neck corresponding to eutopic thyroid hypoplasia. The discovery of a remaining thyroid of less than 1 cm justified the patient survival up to old age.

Analysis of physical and mental development of children with aplasia, hypoplasia and ectopy of the thyroid gland

OBJECTIVE

Evaluation of clinical and biochemical differences between various forms of thyroid dysgenesia in children.

METHODS

The study involved 102 children at the age between 4.8 and 14.2 years who were born with congenital hypothyroidism (CH), as diagnosed by neonatal screening examinations. In all the children diagnosis was settled and the levothyroxine (L-T4) administration was started by the 19th day of life. Out of the examined children, 79 were selected with following three forms of developmental thyroid disorders: Group I--athyroidism (thyroid aplasia or agenesis), Group II--thyroid hypoplasia, Group III--thyroid ectopy. On the basis of neonatal TSH (nTSH) levels obtained by screening and serum TSH, FT4 and Tg concentrations, the severity of hypothyroidism was determined at the time of diagnosis. Physical and mental development of the children was evaluated on the basis of growth and bone age indices and Wechsler's scale, respectively.

RESULTS

Developmental disorders were diagnosed in 79 cases (77.4% CH) which included 45 cases (44.1%) of athyroidism, 31 cases (30.4%) of thyroid hypoplasia and 3 cases (2.9%) of thyroid ectopy. The physical and mental development in the studied groups was evaluated as normal.

CONCLUSIONS

In the group of children with athyroidism, significantly lower growth indices and IQ values were found in comparison with respective values observed in the other study groups. However, the indices of physical and mental development in all the studied groups were within the normal values for children population. An early diagnosis and early administration of hormonal replacement therapy by L-T4 ensure normal development of children with CH, regardless of underlying causes and associated with them severity of congenital hypothyroidism.