Yukari Sugiyama

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.

Successful Treatment of Partial Nephrogenic Diabetes insipidus with Thiazide and Desmopressin

Objective: To clarify whether combination treatment with desmopressin (DDAVP) and thiazide was clinically effective in a patient with congenital nephrogenic diabetes insipidus (CNDI), we evaluated the treatment in a 7-year-old boy with CNDI who had demonstrated a partial response to DDAVP. Method: Both volume of urine and the presence of nocturia were determined during treatment. Result: Neither the usual therapy of a low-salt diet and a thiazide nor intranasal therapy with a large dose of DDAVP was effective. However, combination treatment resulted in a decrease in urinary volume and the disappearance of nocturia. Conclusion: DDAVP coupled with thiazide may be useful for CNDI in patients who have shown a partial response to DDAVP.

Transient hyper-17-OHPnemia unrelated to cross-reactions with residual fetal adrenal cortex products

Objective: To clarify the pathogenesis of transient hyper-17α-hydroxyprogesteronemia, we initiated a laboratory investigation in a pre-term infant with persistently high serum 17α-hydroxyprogesterone (17-OHP) until 2 months of age. Methods: Serum 17-OHP level was measured by high-performance liquid chromatography and radioimmunoassay, and gene analysis of CYP21A2 (21-hydroxylase) was performed. Result: Serum 17-OHP level on the 29th day of life was 25.4 ng/ml, and the urinary steroid profile showed low pregnanetriolone. Gene analysis of 21-hydroxylase disclosed no mutation, and 17-OHP normalized by 3 months of age without specific treatment. Conclusion: Transient elevations in 17-OHP, which do not appear related to cross-reactions with products of a residual fetal adrenal cortex, may occur in the first few months of life.

Elevation of serum creatine kinase in response to medical treatment of Graves’ disease in children: Clinical observation

We describe two cases of increases in serum creatine kinase (CK) concentrations in children undergoing treatment of Graves’ disease with antithyroid medications. Presenting complaints consisted of myalgias and muscle cramping in both patients, and increases in serum CK levels were noted 1 mo after initiation of antithyroid drugs. Both patients were euthyroid at the time of CK elevation. While the mechanisms for this process are not clear, it is likely that the acute decrease of thyroid hormones in tissues following a state of chronic hyperthyroidism may result in relative hypothyroid states and subsequent alterations in CK concentrations.