Hiroki Imamine

Clinical significance of heterozygous carriers associated with compensated hypothyroidism in R450H, a common inactivating mutation of the thyrotropin receptor gene in Japanese.

Loss-of-function mutations in the thyrotropin receptor (TSHR) gene were described as a syndrome characterized by thyroid hyposensivity to biologically active TSH, ranging from euthyroid to severe hypothyroidism. In Japanese, a common mutation in the TSHR gene is R450H, which demonstrated moderately impaired receptor function. We studied six subjects of Japanese origin whose major abnormality was persistent hyperthyrotropinemia by genetic sequence analysis of the TSHR gene. Three subjects were homozygous for the R450H mutation, whereas the three remaining subjects were single heterozygous. Homozygous subjects displayed mild hypothyroidism confirmed by moderately elevated basal TSH levels and excessive TSH response to TRH administration. Heterozygous subjects also demonstrated fully or partially compensated hypothyroidism, but less severe than that of homozygous subjects. More frequent involvement of the R450H mutation in the TSHR gene in Japanese was identified. In addition, a good correlation between phenotype and genotype was demonstrated in respect to biochemical analysis and drug dosage. Our observations showed clinical significance of heterozygosity associated with compensated hypothyroidism in spite of only mildly impaired receptor function.

Longitudinal Evaluation of Patients with a Homozygous R450H Mutation of the TSH Receptor Gene

Background/Aim: The R450H mutation of the TSH receptor (TSHR) gene has been frequently observed in Japanese patients with resistance to TSH. The purpose of this study was to clarify the phenotype of patients with a homozygous R450H mutation of the TSHR gene; the mutant receptor has previously demonstrated moderately impaired function in vitro. Methods: We performed a clinical investigation of 5 Japanese patients who had hyperthyrotropinemia as neonates, in whom a homozygous R450H mutation of the TSHR gene had been demonstrated by genetic sequencing analysis. Results: The thyroid hormone levels of the patients were normal in early infancy, although their serum levels of TSH were mildly elevated. After supplemental treatment with levothyroxine sodium (L-T4) was started, we had to increase the dose to maintain the level of TSH within the normal range in all patients. Thyroid dysfunction became obvious in one patient at reexamination during adolescence when L-T4 treatment was stopped for 1 month. Four patients were examined for intelligence quotient and their scores were normal. Conclusions: Thyroid hormone replacement therapy should be considered based on biological data in patients with hyperthyrotropinemia who have a homozygous R450H mutation of the TSHR gene even if they do not exhibit obvious hypothyroidism in infancy.

Clinical characteristics of eight patients with congenital nephrogenic diabetes insipidus

Congenital nephrogenic diabetes insipidus (NDI) is characterized by the insensitivity of the distal nephron to arginine vasopressin. Clinical knowledge of this disease is based largely on case reports. For this study, we investigated the clinical findings of eight patients in terms of age at onset, age at diagnosis, main complaint, results of physical examination, the diagnosis, the effect of treatment, kidney function, and presence or absence of gene defects. The main complaints of all eight cases at initial examination were unknown fever, failure to thrive, and short stature. Polyuria and polydipsia are not always the chief complaints with congenital NDI. In one case, diabetes insipidus could be diagnosed based only on the results of a 5% hypertonic saline test. In six cases, we found abnormalities in the V2 receptor gene. Initially, trichlormethiazide therapy was shown to have a significant effect on polyuria; however, this effect decreased over time. In one patient with partial NDI, the addition of trichlormethiazide twice a day to 1-desamino-8-d-arginine vasopression increased urine osmolality in the morning and caused nocturia to disappear. Results of 99mTc-diethylenetriamine pentaacetic acid kidney scintigraphy revealed a slight decrease in glomerular filtration rate in three patients. No patient experienced serious renal dysfunction.

The Tei index permits evaluation of cardiopulmonary function during inhaled nitric oxide therapy in the hypoxic newborn piglet.

The purpose of this study was to test the effectiveness of a new Doppler index combining systolic and diastolic time intervals (the Tei index) in the prospective assessment of ventricular function and pulmonary circulation in a newborn piglet model with hypoxic pulmonary hypertension during inhaled nitric oxide (NO). Piglets were prepared for the experiments under normal air, hypoxia, and hypoxia-with-inhaled-NO conditions. Complete two-dimensional Doppler echocardiographic examinations were performed in each condition. The right-ventricle (RV) Tei index increased with hypoxia and decreased following the inhalation of NO. Furthermore, there was a direct correlation between the individual changes in the RV Tei index and individual changes in mean pulmonary arterial pressure in each condition. We conclude that the Tei index is useful for assessing cardiac function and pulmonary circulation in hypoxic pulmonary hypertension during inhaled NO. These results suggest that the Tei index provides an objective assessment of persistent pulmonary hypertension of the newborn.

A Case of a Preterm Infant with 21-Hydroxylase Deficiency: Implications of the Biochemical Diagnosis with Urinary Pregnanetriolone by Gas Chromatography/Mass Spectrometry in Selected Ion Monitoring (GCMS-SIM)

The biochemical diagnosis of 21-hydroxylase deficiency (21-OHD) is difficult in preterm infants. To date, no marker for the biochemical diagnosis of 21-OHD has been found. Seventeen α-hydroxyprogesterone (17-OHP), is not useful because of interference by delta 5 steroids from the fetal adrenal cortex. A 5-d-old female infant, born at 31 wk of gestation, was suspected of having 21-OHD based on physical findings (mild clitoromegaly, pigmentation of the tongue and gingiva) as well as laboratory data (17-OHP >93.5 ng/ml by ELISA 7 prime extractive method in filter paper-dried blood spot and 718.3 ng/ml by RIA after high performance liquid chromatography extraction in serum; plasma ACTH 690 pg/ml; and serum testosterone 3,169 ng/dl). We examined her urinary steroid profiles by gas chromatography/mass spectrometry in selected ion monitoring (GCMS-SIM) at 8 d of age. The pregnanetriolone (Ptl) level was noticeably high (0.80 mg/g creatinine), which was strongly suggestive of 21-OHD. Gene analysis of CYP21A2 showed compound heterozygosity, one allele having a cluster mutation in exon 6 and the other having a large deletion including CYP21A2, confirming the diagnosis of 21-OHD. This case suggested that, in preterm infants, urinary Ptl by GCMS-SIM can be useful for the biochemical diagnosis of 21-OHD.