Patterns of TSH response to TRH in children with hypopituitarism

Congenital Central Hypothyroidism Caused by a Novel IGSF1 Variant Identified in a French Family

INTRODUCTION

Congenital central hypothyroidism (CCH) is a rare disorder that can be caused by X-linked mutations in the immunoglobulin superfamily member 1 (IGSF1) gene. Here, we describe four familial cases with a variable presentation due to a novel IGSF1 pathogenic variant.

CASE PRESENTATION

In the index case, an investigation at birth of a suspected brain-lung-thyroid syndrome surprisingly revealed a central hypothyroidism. Next-generation sequencing uncovered a novel IGSF1 pathogenic variant: a hemizygous single base duplication (G) resulting in a premature stop codon (NM_001555.4: c.2485dup, p.Ala829Glyfs*15). Further family investigations revealed missed neonatal CCH for the older brother who presented with prolonged jaundice (thyroid stimulating hormone 3.06 mUI/L, FT4 9.4 pmol/L, FT3 4.2 pmol/L). It also led to the diagnosis of CCH at 11 months of age for the younger brother, whose thyroid function was considered normal at birth. Neuropsychological evaluations showed no cognitive impairment for the eldest two brothers, but a slightly reduced processing-speed index compared with the other parameters for the oldest. Furthermore, a maternal uncle was diagnosed with biochemical CCH at 34 years of age, despite having few symptoms, and a complete workup revealed prolactin deficiency and macroorchidism.

DISCUSSION

This report of a rare case of neonatal CCH caused by IGSF1 deficiency highlights the importance of recognizing the neonatal signs of hypothyroidism to diagnose CCH as early as possible. Our results also show the importance of performing family genetic screening if a pathogenic variant is identified, to properly monitor carriers as CCH may develop over time. We suggest that these families should be followed up in the long term to better understand the natural history of this syndrome and evaluate the need for hormone substitution.

Thyroid hormones in children with epilepsy during long-term administration of carbamazepine and valproate

OBJECTIVE

This study evaluates the effects of long-term carbamazepine (CBZ) and valproate acid (VPA) therapy on thyroid function in epileptic children.

DESIGN

A prospective study performed in 32 newly diagnosed pediatric patients, subdivided into two groups: 18 patients treated with CBZ and 14 patients treated with VPA. Thirty-two sex- and age- matched subjects served as controls.

METHODS

Serum TSH, thyroxine (T(4)), triiodothyronine (T(3)), free thyroxine (fT(4)), free triiodothyronine (fT(3)), thyroid peroxidase antibodies (TPO-Ab), and thyroglobulin antibodies (TG-Ab) were evaluated at baseline and at the 3rd, 6th, and 12th month in all patients and in the control group. A TRH stimulation test was performed in all epileptic patients at baseline and at the 3rd, 6th, and 12th month evaluations while in controls only baseline assessment was carried out.

RESULTS

At baseline evaluation, thyroid function was normal in all epileptic children. After 3 months, CBZ-treated patients showed serum T(4) and fT(4) levels significantly lower than baseline evaluation and control subjects. Serum T(4) and fT(4) concentrations were unaffected by VPA monotherapy. Serum T(3) and fT(3) were normal in both CBZ-treated and VPA-treated patients. TRH test was normal in all patients. At 6th and 12th month evaluations, the same alterations were present in CBZ-treated patients while thyroid function remained normal in VPA-treated patients. TRH test responses were normal in all epileptic patients. TPO-Ab and TG-Ab were always absent in all patients.

CONCLUSIONS

Our data suggest that VPA monotherapy does not alter thyroid hormones. On the contrary, alterations of thyroid hormones occur in CBZ-treated children. However, the patients are euthyroid and thyroid hormone alterations are not associated with clinical or subclinical hypothyroidism.

Role of the thyrotropin-releasing hormone stimulation test in diagnosis of congenital central hypothyroidism in infants

CONTEXT

A shortage of thyroid hormone during prenatal life and the first years after birth results in a spectrum of neuropsychological disorders, depending on the duration and severity of the deficiency. In the case of congenital hypothyroidism of central origin (CH-C), the majority of patients have multiple pituitary hormone deficiencies (MPHD). This condition poses an additional threat to postnatal central nervous system development, primarily on account of neuroglycopenia due to ACTH/cortisol deficiency with or without additional GH deficiency. Therefore, in CH-C, rapid diagnosis is even more urgent than in congenital hypothyroidism of thyroidal origin.

OBJECTIVE

In the assessment of hypothalamic-pituitary-thyroid function, we considered the pituitary response to iv administration of TRH (TRH test) pivotal. We evaluated the usefulness of the TRH test in a cohort of infants with neonatal congenital hypothyroidism screening results indicative of CH-C by analyzing the results within the framework of investigations of the anatomical and functional integrity of the hypothalamo-hypophyseal system.

DESIGN AND SETTING

The study was a Dutch nationwide prospective study (1994-1996). Patients were included if neonatal congenital hypothyroidism screening results were indicative of CH-C and patients could be tested within 3 months of birth.

PATIENTS

Ten male and five female infants with CH-C, detected by neonatal screening, and six infants with false-positive screening results, nonthyroidal illness, or transient hypothyroidism, were included in the study.

MAIN OUTCOME MEASURES

Results of TRH tests, within the framework of extensive endocrinological examinations and cerebral magnetic resonance imaging, were measured.

RESULTS

All patients with type 3 TSH responses to TRH had MPHD, and the majority (67%) of patients with type 2 responses had isolated TSH deficiency.

CONCLUSIONS

The TRH test has a pivotal role in the diagnosis of TSH deficiency in young infants. Abnormal TRH test results, especially a type 3 response, urge immediate assessment of integral hypothalamic-pituitary function because the majority of patients have MPHD.

An evaluation of the thyrotrophin-releasing hormone stimulation test in paediatric clinical practice

AIM

The aim of this retrospective study was to evaluate the clinical usefulness of the thyrotropin-releasing hormone (TRH) test in children with suspected hypothalamic or pituitary dysfunction.

METHODS

We reviewed the case notes of all patients in whom a TRH test had been performed over a 6-year period. Group 1 (n = 85, 34 males, aged 0.9-18.8 years) was the reference group with no evidence of hypothalamic, pituitary or thyroid dysfunction. Group 2 (n = 42, 24 males, 0.1-18.0 years) were being investigated for possible pituitary or hypothalamic insufficiency.

RESULTS

In Group 1, thyrotropin (TSH) responses were higher in females than males (p < 0.01). In Group 2, TSH responses were normal for gender in 26 patients, subnormal in 5, and exaggerated/delayed in 11. Four patients with normal TSH responses and 4 with exaggerated/delayed responses had persistently low free thyroxine (FT(4)) or later developed low FT(4) and were treated with thyroxine. All those with subnormal TSH responses had normal FT(4) and were not treated. The TRH test did not reliably discriminate between hypothalamic and pituitary disorders.

CONCLUSIONS

The TRH test did not give useful clinical information. Clinical decisions regarding thyroxine treatment were based on FT(4), not the TRH test. The TRH test should be abandoned in paediatric practice.

Neonatal detection of congenital hypothyroidism of central origin

Due to the high frequency of concurrent pituitary hormone deficiencies, congenital hypothyroidism (CH) of central origin (CH-C) is a life-threatening disorder. Yet only a minority of these patients are detected by neonatal CH screening programs worldwide. We conducted a prospective multicenter study involving a 2-yr cohort of neonatally diagnosed CH-C patients to determine whether a T(4)-TSH-based neonatal CH screening protocol extended with T(4) binding globulin determinations improves early detection of CH-C and to assess the extent of pituitary hormone deficiency among the identified CH-C patients. In all infants with screening results indicative of CH-C, the functional integrity of the hypothalamo-hypophyseal system was investigated by dynamic tests; the anatomical integrity was investigated by magnetic resonance imaging. Initial test results were evaluated after 5 yr of follow-up. Among 385,000 infants screened over the 2-yr period, 19 cases of permanent CH-C were detected (prevalence, 1:20,263; 95% confidence interval, 1:12,976 to 1:33,654), representing 13.5% of all detected cases of permanent CH. The majority (78%) had multiple pituitary hormone deficiency, whereas 53% had pituitary malformations on magnetic resonance imaging. We conclude that infants with CH-C can very well be detected by neonatal screening. The estimated prevalence and the severity of pituitary dysfunction of this treatable disorder call for explicit attention for this entity of CH in neonatal screening programs worldwide.

Is the thyrotropin-releasing hormone test necessary in the diagnosis of central hypothyroidism in children

To determine the value of the TRH test, we analyzed the unstimulated serum T(4) and TSH concentrations in 54 children with central hypothyroidism. A TRH test was performed in 30 patients. Midline brain defects (septo-optic dysplasia, 28; holoprosencephaly, 2) and combined pituitary hormone deficiencies were present in 30 and 52 patients, respectively. The mean serum free T(4), total T(4), and basal TSH concentrations were 0.6 ng/dl, 4.0 microg/dl, and 2.8 microU/ml, respectively. Five patients demonstrated elevated basal serum TSH concentrations. A normal TRH test [increase (delta) in TSH, 4.5-17.8], based on data from 30 controls, was documented in 23.3% of patients. Brisk (deltaTSH, >17.8), absent/blunted (deltaTSH, <4.5), and delayed responses were documented in 16.7%, 30%, and 30% of patients, respectively. The mean age at diagnosis was 2.8 yr, with 8 patients evolving into TSH deficiency. It was not possible to differentiate patients as having pituitary or hypothalamic disease based solely on the TRH test results. Patients with septo-optic dysplasia were diagnosed earlier and had elevated basal serum TSH and PRL concentrations, diabetes insipidus, and evolving disease. Although full pituitary function assessment is mandatory to identify combined pituitary hormone deficiencies, a TRH test is not essential, and the diagnosis should be made by serial T(4) measurements.

The combined pituitary function test in children: an evaluation of the clinical usefulness of TRH and LHRH stimulation tests through a retrospective analysis of one hundred and twenty six cases

OBJECTIVE

The combined pituitary function test is routinely used in the endocrine investigation of short children. The TRH and luteinising hormone-releasing hormone (LHRH) response tests have been shown to be of minimal value in adults. We have evaluated the clinical utility of these tests in the context of combined pituitary function testing in children.

DESIGN

A retrospective analysis of basal hormone measurements and pituitary stimulation tests in relation to clinical assessment of pituitary function.

PATIENTS

One hundred and twenty-six children, 82 boys and 44 girls, aged 2-17 years, who had undergone pituitary function testing were studied.

RESULTS

The TSH response to TRH stimulation correlated directly with basal plasma TSH but not basal plasma total T4. In patients with an impaired response to stimulation, basal TSH concentrations were <2.0 mIU/l and significantly lower than in patients with a normal response (P < 0.0001). An impaired response to TRH stimulation had a positive predictive value of 0.43 and a negative predictive value of 0.90 for the diagnosis of hypopituitarism. A basal TSH concentration of <2.0 mIU/l had a positive predictive value of 0.22 and a negative predictive value of 0.92. A low basal T4 (normal range 60-140 nmol/l) in combination with an inappropriately low or normal basal TSH was always associated with a diagnosis of hypopituitarism. The responses of plasma LH and FSH to LHRH stimulation correlated directly with basal plasma LH and FSH concentrations. Basal gonadotrophin concentrations, basal sex hormone concentrations or response to LHRH stimulation could not distinguish patients with constitutional delay of growth and puberty from those with hypopituitarism. There was no apparent relationship between either basal gonadotrophin concentrations or response to LHRH stimulation and clinical assessment of pituitary function. In patients ≥13 years with constitutional delay of growth and puberty the median and interquartile ranges of basal LH and FSH were 1.4 IU/l (0.7-3.6) and 2.6 IU/l (2.2-5.2) respectively. The three hypopituitary patients in this study with chronological age ≥13 years had undetectable concentrations of both gonadotrophins. The response of LH and FSH to LHRH stimulation was significantly lower in patients ≥13 years with clinical hypopituitarism than in those with intact pituitary function (P <0.02).

CONCLUSION

TRH and LHRH tests in children with short stature appear to have little value over and above the baseline hormone measurements. An abnormal response to hormone stimulation is not diagnostic of hypothalamic-pituitary disease. We have demonstrated that neither TRH nor LHRH stimulation tests should be routinely used in the investigation of children with short stature.

Hypothalamic-pituitary thyroid abnormalities in children after renal transplantation

Patients with a successful renal transplant may have abnormalities in thyroid function. We evaluated serum thyroid hormone levels, serum thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH), and the circadian pattern of serum TSH in 18 children aged 6.6-19.4 years (median 12.6 years), 4.0 +/- 2.9 years after renal transplantation. In 14 children, immunosuppressive therapy included methylprednisone [mean (+/-SD) 0.17 +/- 0.05 mg/ kg per day], while in 11 it included deflazacort (0.32 +/- 0.1 mg/kg per day). Seven children were studied twice, under methylprednisone and again while on deflazacort therapy. Mean total and free thyroxine (T4) values were significantly below the mean control levels (total T4 108.5 +/- 21.5 vs. 118.7 +/- 22.1 nmol/l, P < 0.05 and free T4 14.4 +/- 4.0 vs. 18 +/- 4.9 pmol/l, P < 0.001). Morning basal TSH levels were within the normal range. The mean TSH increment after TRH was 4.4 +/- 3.5 mU/l, significantly lower than that of controls (10.8 +/- 4.26, P < 0.001). Of 7 patients on methylprednisone, 4 had nocturnal TSH surges below the normal range (95% confidence limits 47%-300%); this occurred in 3 of 8 patients on deflazacort therapy. The TSH response to TRH was correlated with deflazacort dose. Patients on methylprednisone and deflazacort therapy had similar thyroid alterations. Our findings support the hypothesis that after renal transplantation some children have hypothalamic-pituitary thyroid abnormalities in which glucocorticoids may play a significant role.

Thyroid function and serum IGF-1 in children before and after liver transplantation

We report results of serum thyroid hormone and IGF-1 concentrations in 20 children, 1.2 to 13.6 years old, with various degrees of chronic liver dysfunction (CLD), before and after successful orthotopic liver transplantation (OLT). Ten children presented with moderate chronic liver disease (CLD-M) with prothrombin time (PT) > 50% and serum albumin concentration > 3 g/dl; 7 children had severe chronic liver disease (CLD-S) with PT < 50% and serum albumin concentration < 3 g/dl; and 7 children who had received an OLT, who had normal liver function at the time of the study. Four of the latter group were also studied before OLT. Patients with CLD-M had normal mean +/- SD serum levels of total T3 (2.0 +/- 0.7 nmol/l), total T4 (125 +/- 25.9 nmol/l) and fT4 concentrations (16 +/- 2.8 pmol/l). In contrast, children with CLD-S showed a significant decrease in thyroid hormones together with normal basal TSH values (T3 0.8 +/- 0.0 nmol/l; T4 45.6 +/- 19.5 nmol/l; fT4 7.4 +/- 1.1 pmol/l; TSH 3.8 +/- 0.9 mU/l). Patients who received a successful OLT showed mean peripheral thyroid hormone concentrations significantly higher than CLD-S patients (T3 1.7 +/- 0.7 nmol/l, p < 0.005; T4 92.8 +/- 18.2 nmol/l, p < 0.001; fT4 14.5 +/- 3.1 pmol/l, p < 0.001). A significant correlation was found between thyroid hormone levels and PT or serum albumin. In the nine patients with CLD-M and CLD-S in whom serum IGF-1 concentration was measured, values found (mean +/- SD 0.08 +/- 0.05 U/ml) were below the 95% confidence limit of matched controls.

Evidence of hypothalamic-pituitary thyroid abnormalities in children with end-stage renal disease

Patients with end-stage renal disease may have abnormalities of growth and of gonadal and thyroid hormones, so we attempted to determine the mechanisms that may be involved in the altered thyroid function. We evaluated serum thyroid hormone levels, their changes immediately after hemodialysis, the serum thyrotropin (thyroid-stimulating hormone (TSH) response to thyrotropin releasing hormone, and the circadian pattern of serum TSH in nine children with end-stage renal disease who were between 7 1/2 years and 17 years 1 month of age. Seven patients had been receiving hemodialysis for a median of 3.3 years; the other two were receiving continuous ambulatory peritoneal dialysis. Four patients had low serum total thyroxine (T4) values, and all nine had low free T4 values. Mean concentrations of total T4, free T4, and total triiodothyronine (T3), which were significantly less than normal before hemodialysis, returned to normal levels immediately after dialysis. Postdialysis thyroid hormone increases did not correlate with the decrease in weight or the increase in hematocrit observed immediately after dialysis. All but one patient had basal TSH levels within the normal range. Three patients had a deficient TSH response to thyrotropin releasing hormone, and the TSH response was prolonged in all of them. The mean (+/- SD) nocturnal TSH surge was 50 +/- 68%. Five of the eight patients studied had a nocturnal TSH surge below the normal range (95% confidence limits 47% to 300%). Serum free T4 values correlated with the TSH nocturnal surge (r, 0.73; p less than 0.05). Our findings support the hypothesis that some patients with end-stage renal disease have central hypothyroidism.

Thyroid dysfunction in Hodgkin's disease

Radiotherapy to the neck and/or polychemotherapy late effects on the thyroid were investigated in 51 patients (34 males and 17 females) with Hodgkin's disease. Except for two untreated, recently diagnosed patients, all were studied after 1 to 105 months (median, 27.5 months) of completion of polychemotherapy. Age ranged from 6.2 to 36.6 years (median, 13.6 years). Patients were divided according to treatment into four groups: (A) patients treated with CVPP (cyclophosphamide, vinblastine, procarbazine, and prednisone); (B) 22 patients treated with CVPP plus radiotherapy (median radiation dose to the thyroid, 3000 cGy); (C) seven patients with ACOP/BVP (adriamycin, cyclophosphamide, vincristine, prednisone, bleomycin, vinblastine, procarbazine); and (D) seven patients treated with different polychemotherapy protocols, four of whom also received radiotherapy. Elevated basal and/or post-TRH, -TSH levels were found in the following: Group A: two of 12 patients (17%); Group B: 11 of 22 (50%); Group C: four of seven (57%); and Group D: two of seven (28%). Positive antimicrosomal thyroid antibody titers (AM Ab) were found in the following: Group A: three of 12 patients (25%); Group B: six of 21 (28%), Group C: two of seven (28%); and Group D: one of six (17%). Of 46 patients studied, 12 (26%) had positive AM Ab; 37 of 46 patients were younger than 20 years of age, 11 (30%) of whom had positive AM Ab versus 4% in the normal population (P less than 0.001). Two recently diagnosed, untreated patients had either high TSH response to TRH or positive AM Ab. In conclusion, higher frequency of thyroid dysfunction was observed in patients receiving radiotherapy (50% versus 27%). Prevalence of positive AM Ab, apparently unrelated to therapy, was higher in young patients than in the normal population. A predisposition to autoimmune thyroid disease seems to be present in these patients, but it is not possible to discern how lymphoma and thyroiditis are interrelated.

Long-term endocrine sequelae after surgery, radiotherapy, and chemotherapy in children with medulloblastoma

Thirteen children with medulloblastoma, were studied after 2 to 62 months off radiotherapy and chemotherapy with methotrexate and BCNU. Ages at time of study ranged from 2.3 to 15.7 years. Eleven patients, followed for a mean of 22 months, showed a significant decrease of height score, whereas nine patients had deficient growth hormone (GH) response to provocative tests. Clinical pubertal progression was normal in all patients, and three of five girls with advanced pubertal development had menarche. No evidences of gonadotropin disturbances were found in five patients whereas seven had raised basal follicle-stimulating hormone (FSH) level or FSH response to luteinizing hormone-releasing hormone (LH-RH). Abnormalities in thyrotrophin (TSH) secretion were found in 9 of 13 patients. This study shows that poor growth and GH deficiency were frequent in our patients. The high frequency of thyroid disturbances observed point out the need of evaluating thyroid function for adequate replacement therapy. Perhaps modification of adjuvant chemotherapy in the future can diminish drug-induced gonadal damage.

Familial growth retardation with isolated thyroid-stimulating hormone deficiency

Three brothers with isolated thyroid-stimulating hormone (TSH) deficiency were observed at ages 17, 15, and 10 years. They suffered from severely retarded growth, with a marked retardation in bone maturation. Their serum T4, T3, and TSH levels were low. Serum thyrotropin-releasing hormone (TRH) concentration was normal. No increases in TSH levels were elicited during the TRH test. The other pituitary hormones, adrenocorticotropic hormone, growth hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin hormone, responded normally to stimulation. Thyroxin treatment triggered a growth acceleration. Genetic investigation revealed several instances of small stature on the father's side.

Response to TRH in suspected hypopituitarism

A retrospective analysis was made of 405 thyrotrophin-releasing hormone (TRH) stimulation tests on children who were successful applicants for growth hormone (GH) therapy in the UK between 1977 and 1981 inclusive. Thyroid-stimulating hormone (TSH) responses to TRH were divided into normal and those indicating pituitary or hypothalamic disease on the basis of criteria which eliminated variation in TSH assay between laboratories. Among children known to be hypothyroid 93% had abnormal TRH stimulation tests, but 35% of those children who were clinically euthyroid and who had normal serum thyroxin levels also had abnormal TSH responses to TRH. Abnormal TRH tests in the latter group were most common in euthyroid children who had GH deficiency with clearly defined aetiology and least common in those with idiopathic GH deficiency. Further work is required to clarify the interpretation of an abnormal TRH stimulation test in this group of children, but until this is done, such patients should be kept under regular review with respect to thyroid function.