[Thyroid hormone and skeletal metabolism].

The role of the hypothalamic-pituitary-thyroid axis is important in normal skeletal development, gain of bone mass, and regulation of adult bone metabolism. Hypothyroidism in childhood causes delayed bone maturation and growth disturbance and thyroid dysfunction in adult induces altered bone remodeling and an increased risk of bone fracture. Thyroid hormone actions in skeletal cells are mainly mediated by thyroid hormone receptor α (TRα) . The responses to thyroid hormone are regulated by type 2 and 3 iodothyronine deiodinase (DIO2 and DIO3) , which convert prohormone (T4) to active hormone (T3) . Euthyroid status is necessary for the homeostasis of human bone metabolism.

STR mutations on chromosome 15q cause thyrotropin resistance by activating a primate-specific enhancer of MIR7-2/MIR1179.

Thyrotropin (TSH) is the master regulator of thyroid gland growth and function. Resistance to TSH (RTSH) describes conditions with reduced sensitivity to TSH. Dominantly inherited RTSH has been linked to a locus on chromosome 15q, but its genetic basis has remained elusive. Here we show that non-coding mutations in a (TTTG)4 short tandem repeat (STR) underlie dominantly inherited RTSH in all 82 affected participants from 12 unrelated families. The STR is contained in a primate-specific Alu retrotransposon with thyroid-specific cis-regulatory chromatin features. Fiber-seq and RNA-seq studies revealed that the mutant STR activates a thyroid-specific enhancer cluster, leading to haplotype-specific upregulation of the bicistronic MIR7-2/MIR1179 locus 35 kb downstream and overexpression of its microRNA products in the participants' thyrocytes. An imbalance in signaling pathways targeted by these micro-RNAs provides a working model for this cause of RTSH. This finding broadens our current knowledge of genetic defects altering pituitary-thyroid feedback regulation.

[Monogenic obesity in human].

Obesity is a heterogeneous pathologic condition that is driven by interactions between multiple genetic and environmental factors. The discovery of leptin has provided the useful clue to the molecular dissection of central pathways involved in the regulation of food intake and body weight. Monogenic obesity in human has been documented. Several obesity causing genes within the leptin-POMC-melanocortin axis have been identified: Leptin, leptin receptor, proopiomelanocortin (POMC), prohormone convertase 1 (PC1), and melanocortin receptor-4 (MC4-R) genes. The patients who have a mutation of such genes developed early onset of obesity and distinct metabolic abnormalities. Also, several gene mutations have been identified in some syndromes presenting hereditary symptomatic obesity.

Background factors associated with academic motivation for attending medical school immediately after admission in Japan: A single-center study.

Background: To become a doctor with a high level of professionalism and ethical standards, it is important to have and maintain a high level of motivation right from medical school. However, studies in Japan have not quantitatively investigated the factors related to motivation immediately after enrollment. This study aimed to identify the demographic factors that influence the motivation of medical students immediately after admission. Methods: A cross-sectional single-center study was conducted. First-year medical students answered our questionnaire three weeks after the admission. The questionnaire comprised 16 demographic items and the 28-item Academic Motivation Scale, which was used to quantify motivation. Results: Our analysis showed that amotivation, representing low levels of self-determinant motivation, was significantly higher in students whose parents were medical professionals and in students who did not talk about their problems than in those whose parents were not medical professionals and those who did talk about their problems. Intrinsic motivation, which indicates the level of self-determinant motivation, was significantly lower in students who belonged to a sports club. Conclusions: We suggest that having parents who are medical professionals may be associated with an individual's decreased motivation when entering medical school in Japan. Though this is a novel finding, further research is needed to analyze this relationship.

Japan's Academic Barriers to Gender Equality as Seen in a Comparison of Public and Private Medical Schools: A Cross-Sectional Study.

Background: Gender inequalities persist in Japanese academic medicine. Some public medical schools have introduced various types of career support for women physicians, whereas few private schools have. Few studies describe the representation of women at different academic ranks and adequacy of career support in public and private medical schools in Japan. Study Design: Cross-sectional descriptive study. Methods: We used publicly available data from the 2018 National Survey on Career Support for Japanese Women Physicians published by the Association of Japanese Medical Colleges in March 2019, which was answered by departments regarding supporting women physicians. Participants represented 51 public and 29 private medical schools in Japan. The proportion of women at academic ranks and career support availability in private and public medical schools were determined using chi-squared test or Fisher's exact test. Results: The proportion of women in senior ranks was significantly higher in private (28.2%) than in public medical schools (25.4%) (p < 0.001). Excluding associate professors, the proportion of professors, lecturers, and assistant professors was significantly higher in private medical schools (3.8% vs. 5.8%, p = 0.002; 12.2% vs. 16.0%, p < 0.001; 20.5% vs. 29.9%, p < 0.001). More public medical schools provided position support and support for other job aspects (43.1% vs. 20.7%, p = 0.043; 70.6% vs. 20.7%, p < 0.001). Conclusions: Public medical schools have lower proportions of women in the academic hierarchy but provide more career support than do private medical schools. Further study is needed to reveal the possible causes of this pattern.

Cognitive Bias and Diagnostic Errors among Physicians in Japan: A Self-Reflection Survey.

This cross-sectional study aimed to clarify how cognitive biases and situational factors related to diagnostic errors among physicians. A self-reflection questionnaire survey on physicians' most memorable diagnostic error cases was conducted at seven conferences: one each in Okayama, Hiroshima, Matsue, Izumo City, and Osaka, and two in Tokyo. Among the 147 recruited participants, 130 completed and returned the questionnaires. We recruited primary care physicians working in various specialty areas and settings (e.g., clinics and hospitals). Results indicated that the emergency department was the most common setting (47.7%), and the highest frequency of errors occurred during night-time work. An average of 3.08 cognitive biases was attributed to each error. The participants reported anchoring bias (60.0%), premature closure (58.5%), availability bias (46.2%), and hassle bias (33.1%), with the first three being most frequent. Further, multivariate logistic regression analysis for cognitive bias showed that emergency room care can easily induce cognitive bias (adjusted odds ratio 3.96, 95% CI 1.16-13.6, p-value = 0.028). Although limited to a certain extent by its sample collection, due to the sensitive nature of information regarding physicians' diagnostic errors, this study nonetheless shows correlations with environmental factors (emergency room care situations) that induce cognitive biases which, in turn, cause diagnostic errors.

Survey of potentially inappropriate prescriptions for common cold symptoms in Japan: A cross-sectional study.

BACKGROUND: Common cold is among the main reasons patients visit a medical facility. However, few studies have investigated whether prescriptions for common cold in Japan comply with domestic and international evidence. OBJECTIVE: To determine whether prescriptions for common cold complied with domestic and international evidence. METHODS: This cross-sectional study was conducted between October 22, 2020, and January 16, 2021. Patients with cold symptoms who visited the two dispensing pharmacies and met the eligibility criteria were interviewed. MAIN OUTCOME MEASURE: The pharmacists at each store and a physician classified the patients into two groups: the potentially inappropriate prescribing group and the appropriate prescribing group. RESULTS: Of the 150 selected patients, 14 were excluded and 136 were included in the analysis. Males accounted for 44.9% of the total study population, and the median patient age was 34 years (interquartile range [IQR], 27-42). The prevalence rates of potentially inappropriate prescriptions and appropriate prescriptions were 89.0% and 11.0%, respectively and the median drug costs were 602.0 yen (IQR, 479.7-839.2) [$5.2 (IQR, 4.2-7.3)] and 406.7 yen (IQR, 194.5-537.2) [$3.5 (IQR, 1.7-4.7)], respectively. The most common potentially inappropriate prescriptions were the prescription of oral cephem antibacterial agents to patients who did not have symptoms of bacterial infections (50.4%) and ß2 stimulants to those who did not have respiratory symptoms due to underlying disease or history (33.9%). CONCLUSIONS: Approximately 90% of prescriptions for common cold symptoms in the area were potentially inappropriate. Our findings could contribute to the monitoring of the use of medicines for the treatment of common cold symptoms.

The Utility of Virtual Patient Simulations for Clinical Reasoning Education.

Virtual Patient Simulations (VPSs) have been cited as a novel learning strategy, but there is little evidence that VPSs yield improvements in clinical reasoning skills and medical knowledge. This study aimed to clarify the effectiveness of VPSs for improving clinical reasoning skills among medical students, and to compare improvements in knowledge or clinical reasoning skills relevant to specific clinical scenarios. We enrolled 210 fourth-year medical students in March 2017 and March 2018 to participate in a real-time pre-post experimental design conducted in a large lecture hall by using a clicker. A VPS program (®Body Interact, Portugal) was implemented for one two-hour class session using the same methodology during both years. A pre-post 20-item multiple-choice questionnaire (10 knowledge and 10 clinical reasoning items) was used to evaluate learning outcomes. A total of 169 students completed the program. Participants showed significant increases in average total post-test scores, both on knowledge items (pre-test: median = 5, mean = 4.78, 95% CI (4.55-5.01); post-test: median = 5, mean = 5.12, 95% CI (4.90-5.43); p-value = 0.003) and clinical reasoning items (pre-test: median = 5, mean = 5.3 95%, CI (4.98-5.58); post-test: median = 8, mean = 7.81, 95% CI (7.57-8.05); p-value < 0.001). Thus, VPS programs could help medical students improve their clinical decision-making skills without lecturer supervision.

Factors and impact of physicians' diagnostic errors in malpractice claims in Japan.

BACKGROUND: Diagnostic errors are prevalent and associated with increased economic burden; however, little is known about their characteristics at the national level in Japan. This study aimed to investigate clinical outcomes and indemnity payment in cases of diagnostic errors using Japan's largest database of national claims. METHODS: We analyzed characteristics of diagnostic error cases closed between 1961 and 2017, accessed through the national Japanese malpractice claims database. We compared diagnostic error-related claims (DERC) with non-diagnostic error-related claims (non-DERC) in terms of indemnity, clinical outcomes, and factors underlying physicians' diagnostic errors. RESULTS: All 1,802 malpractice claims were included in the analysis. The median patient age was 33 years (interquartile range = 10-54), and 54.2% were men. Deaths were the most common outcome of claims (939/1747; 53.8%). In total, 709 (39.3%, 95% CI: 37.0%-41.6%) DERC cases were observed. The adjusted total billing amount, acceptance rate, adjusted median claims payments, and proportion of deaths were significantly higher in DERC than non-DERC cases. Departments of internal medicine and surgery were 1.42 and 1.55 times more likely, respectively, to have DERC cases than others. Claims involving the emergency room (adjusted odds ratio [OR] = 5.88) and outpatient office (adjusted OR = 2.87) were more likely to be DERC than other cases. The initial diagnoses most likely to lead to diagnostic error were upper respiratory tract infection, non-bleeding digestive tract disease, and "no abnormality." CONCLUSIONS: Cases of diagnostic errors produced severe patient outcomes and were associated with high indemnity. These cases were frequently noted in general exam and emergency rooms as well as internal medicine and surgery departments and were initially considered to be common, mild diseases.

Molecular and clinical findings and their correlations in Silver-Russell syndrome: implications for a positive role of IGF2 in growth determination and differential imprinting regulation of the IGF2-H19 domain in bodies and placentas.

Silver-Russell syndrome (SRS) is characterized by growth failure and dysmorphic features and is frequently caused by hypomethylation (epimutation) of the H19-DMR. Although molecular and clinical studies have extensively been performed for SRS patients themselves, such studies have not been carried out for placentas. We identified 20 epimutation-positive and 40 epimutation-negative Japanese SRS patients and obtained placental weight data from 12 epimutation-positive and ten epimutation-negative patients and paraffin-embedded placental tissues for molecular and histological examinations from three epimutation-positive and two epimutation-negative patients. Methylation patterns were comparable between leukocytes and placentas in both epimutation-positive and epimutation-negative patients. Epimutations resulted in virtually no IGF2 expression and biallelic slight H19 expression in the leukocytes and obviously reduced IGF2 expression of paternal origin and nearly normal H19 expression of maternal origin in the placentas. Epimutation-positive patients had characteristic body phenotype and small placentas with hypoplastic chorionic villi, and epimutation-negative patients had somewhat small placentas with hypoplastic chorionic villi or massive infarction. Furthermore, significant correlations were identified between the H19-DMR methylation index and the body and placental sizes and between the placental weight and the body size in the epimutation-positive patients, whereas such correlations were not detected for the head circumference. These results suggest (1) characteristic phenotype and reduced IGF2 expression in the epimutation-positive placentas; (2) similarities and differences in the epigenetic control of the IGF2-H19 domain between leukocytes and placentas; (3) a positive role of the IGF2 expression level, as reflected by the methylation index, in the determination of body and placental growth in epimutation-positive patients, except for the brain where IGF2 is expressed biallelically; (4) involvement of placental dysfunction in prenatal growth failure; and (5) relevance of both (epi)genetic factor(s) and environmental factor(s) to SRS in epimutation-negative patients.

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.

Primary care doctor fostering and clinical research training in Sweden: Implications for Japan.

In 2018, a new training program for primary care physicians was launched in Japan. As physicians responsible for the training of new primary care physicians, we have faced many problems, particularly in rural areas. The influence of this new program on primary care physicians in rural areas of Japan has not been sufficiently investigated. The aim of this research was to improve training for primary care physicians in Japan by examining training programs in Sweden, where the population challenges are similar to those seen in Japan. In this paper, we will express our opinions and describe the differences in the primary care fostering systems and clinical research training for generalist in Japan and Sweden.

Biallelic inactivation of the dual oxidase maturation factor 2 (DUOXA2) gene as a novel cause of congenital hypothyroidism.

CONTEXT: Dual oxidase 2 (DUOX2) is the catalytic core of the H(2)O(2) generator crucial for the iodination of thyroglobulin in thyroid hormone synthesis. DUOX2 deficiency produces congenital hypothyroidism (CH) in humans and mice. We recently cloned a novel gene, the product of which (dual oxidase maturation factor 2; DUOXA2) is required to express DUOX2 enzymatic activity. OBJECTIVE: Our objective was to identify DUOXA2 mutations as a novel cause of CH due to dyshormonogenesis. PATIENTS: Subjects included 11 CH patients with partial iodine organification defect but negative for other known genetic causes of partial iodine organification defect. RESULTS: One Chinese patient born to nonconsanguineous parents was homozygous for a nonsense mutation (p.Y246X), producing a truncated DUOXA2 protein lacking transmembrane helix 5 and the C-terminal cytoplasmic domain. The mutant protein was inactive in reconstituting DUOX2 in vitro. Pedigree analysis demonstrated recessive inheritance, because heterozygous carriers had normal thyroid function including negative results in neonatal TSH screening. One heterozygous carrier of Y246X was identified in unrelated Chinese controls (n = 92) but not in Caucasian or Japanese controls, indicating that homozygosity for Y246X could be a frequent cause of CH in Chinese. Functional studies suggest that the DUOXA2 paralog (DUOXA1) can partially compensate DUOXA2 deficiency, consistent with the proband having a milder CH phenotype than patients with biallelic DUOX2 nonsense mutations. CONCLUSIONS: We report the first mutation in DUOXA2, identified in a patient with CH and dyshormonogenic goiter. Results of our studies provide evidence for the critical role of DUOXA2 in thyroid hormonogenesis. Biallelic DUOXA2 mutations are a novel genetic event in permanent CH.

Gradual improvement of liver function after administration of ursodeoxycholic acid in an infant with a novel ABCB11 gene mutation with phenotypic continuum between BRIC2 and PFIC2.

OBJECT: The authors report the case of a boy with PFIC type 2 or BRIC type 2 who suffered from liver dysfunction at 2 months after birth. METHODS AND RESULTS: A liver biopsy specimen revealed mild liver cirrhosis, and the findings resembled those observed in Byler disease. Genetic examination revealed a normal familial intrahepatic cholestasis-1 gene, but a heterozygous mutation for the ABCB11, C1620A (F540L), was observed. Therefore, the patient was initially diagnosed with PFIC type 2. For 3 years after the diagnosis, he had severe pruritus, an increased serum bile acid, and normal serum values of gamma-glutamyl transaminase. At the age of 2, treatment with administration of ursodeoxycholic acid was started; subsequently, a gradual improvement in his liver function was observed. At the age of 3, he suffered from massive intestinal and pulmonary hemorrhage, which improved immediately after the administration of vitamin K. He was then admitted to our hospital for liver transplantation. At 1 month after the admission, his liver dysfunction showed further improvement, except for a mild increase in the serum bile acid level. This condition did not show any change during the 5-year follow-up period. In addition, the patient showed severe growth failure and was diagnosed with growth hormone deficiency. Hence, he receives growth hormone administration. CONCLUSION: The patient could be genetically diagnosed with bile salt export pump disease of PFIC type 2 or BRIC type 2. Various clinical features are observed in PFIC or BRIC patients with ABCB11 mutation.

A case of an infant with congenital combined pituitary hormone deficiency and normalized liver histology of infantile cholestasis after hormone replacement therapy.

Congenital combined pituitary hormone deficiency (CPHD) may present with cholestasis in the neonate or during early infancy. However, its precise mechanism is unknown. A 3-mo-old boy presented with cryptorchidism and hypoplastic scrotum after birth. Neonatal jaundice was noted but temporarily improved with phototherapy. Jaundice recurred at 2 mo of age. Elevated direct bilirubin (D-Bil) and liver dysfunction were found but cholangiography showed no signs of biliary atresia (BA). Liver biopsy findings showed giant cell formation of hepatocytes with hypoplastic bile ducts. Subsequent magnetic resonance imaging (MRI) of the head revealed a hypoplastic pituitary gland with an ectopic posterior lobe, and the patient was diagnosed with congenital CPHD based on decreased secretion of cortisol and GH by the pituitary anterior lobe load test. D-Bil levels promptly improved after hydrocortisone (HDC) replacement. We subsequently began replacement with levothyroxine (L-T4) and GH, and liver histology showed normal interlobular bile ducts at 8 mo old. This is the first case report of proven histological improvement after hormone replacement therapy. This suggested that pituitary-mediated hormones, especially cortisol, might be involved in the development of the bile ducts.

Identification and functional analysis of novel inactivating thyrotropin receptor mutations in patients with thyrotropin resistance.

OBJECTIVE: We identified and analyzed novel thyrotropin (TSH) receptor mutations in three Japanese families with resistance to TSH. DESIGN: The TSH receptor gene was sequenced and the mutations were determined. The mutant TSH receptors were transfected into COS-7 cells, and their functions were analyzed. PATIENTS: The patients were compound-heterozygotes for the R450H mutation and novel mutations in the TSH receptor gene. The first patient was a compound-heterozygote for R450H and V473I. The second sibling possessed R450H and R519C. The third sibling had R450H and R519G. RESULTS: The R450H mutant exhibited moderately impaired receptor functions and a moderately decreased cell surface expression in agreement with previous results. The V473I mutant exhibited an almost normal TSH binding, a slightly decreased cyclic adenosine monophosphate (cAMP) response, a moderately decreased inositolphosphate (IP) response, and an almost normal cell surface expression. TSH binding and TSH stimulation of cAMP and IPs were markedly decreased in the R519C and R519G mutants. Cell surface expression was decreased in the R519C mutant and negligible in the R519G mutant. All of these mutants showed normal intracellular synthesis of TSH receptors. CONCLUSIONS: These novel inactivating mutations contribute to understanding of the structure-function relationship of the TSH receptor. To date, all of the patients with TSH resistance resulting from TSH receptor mutations identified in Japan possessed the R450H mutation at least in one allele. These observations suggest that the R450H mutation is a commonly observed TSH receptor mutation in patients with TSH resistance in Japan.

Association of the CTLA-4 gene 49 A/G polymorphism with type 1 diabetes and autoimmune thyroid disease in Japanese children.

OBJECTIVE: To clarify the role of the T-lymphocyte-associated-4 (CTLA-4) polymorphism in the susceptibility to child-onset type 1 diabetes with regard to its clinical characteristics and complications with autoimmune thyroid disease (AITD) in the Japanese population. RESEARCH DESIGN AND METHODS: The CTLA-4 49 A/G polymorphism was detected by the PCR-restriction fragment-length polymorphism (RFLP) method in 97 type 1 diabetic subjects and 20 patients with Graves' disease, a cohort which included 4 patients who also had type 1 diabetes. RESULTS: The genotypes and allele frequencies of this polymorphism did not differ between the type 1 diabetic subjects and the control subjects. The G allele frequency was 63.9% in the type 1 diabetic subjects. The G allele frequency in the subgroup of patients with a high titer of autoantibodies to the GAD antibody (Ab) was 72.9% (P = 0.0499 vs. control subjects); in the subgroup of patients without HLA DRB1*0405, it was 72.6% (P = 0.0271 vs. control subjects); and in the subgroup of patients with a residual beta-cell function, it was 78.6% (P = 0.0391 vs. control subjects). The G allele frequency in the patients with Graves' disease was also significantly higher at 78.1% (P = 0.0405 vs. control subjects). Furthermore, the frequency in our diabetic subjects complicated with Graves' disease was even higher (87.5%). CONCLUSIONS: We have demonstrated that a distinct association exists between the G allele of CTLA-4 and high values of GAD Ab, residual beta-cell function, and the absence of HLA-DRB1*0405.

Guidelines for diagnosis and treatment of 21-hydroxylase deficiency (2014 revision).

Purpose of developing the guidelines: The first guidelines for diagnosis and treatment of 21-hydroxylase deficiency (21-OHD) were published as a diagnostic handbook in Japan in 1989, with a focus on patients with severe disease. The "Guidelines for Treatment of Congenital Adrenal Hyperplasia (21-Hydroxylase Deficiency) Found in Neonatal Mass Screening (1999 revision)" published in 1999 were revised to include 21-OHD patients with very mild or no clinical symptoms. Accumulation of cases and experience has subsequently improved diagnosis and treatment of the disease. Based on these findings, the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology further revised the guidelines for diagnosis and treatment. Target disease/conditions: 21-hydroxylase deficiency. Users of the guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, referring pediatric practitioners, general physicians; and patients.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision).

Purpose of developing the guidelines: Mass screening for congenital hypothyroidism started in 1979 in Japan, and the prognosis for intelligence has been improved by early diagnosis and treatment. The incidence was about 1/4000 of the birth population, but it has increased due to diagnosis of subclinical congenital hypothyroidism. The disease requires continuous treatment, and specialized medical facilities should make a differential diagnosis and treat subjects who are positive in mass screening to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, new findings on prognosis and problems in the adult phase have emerged. Based on these new findings, the 1998 guidelines were revised in the current document (hereinafter referred to as the Guidelines). Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring patients to pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.

Frequencies of spontaneous breast development and spontaneous menarche in Turner syndrome in Japan.

The Growject® database on human GH treatment in Turner syndrome was analyzed in the Turner Syndrome Research Collaboration, and the relationships of the frequencies of spontaneous breast development and spontaneous menarche with karyotype and GH treatment were investigated. One hundred and three cases started GH treatment with 0.5 IU/kg/ week (0.5 IU group), and their dose was increased to 0.35 mg/kg/wk midway through the treatment course. Another 109 cases started GH at a dose of 0.35 mg/kg/wk (0.35 mg group). Spontaneous breast development was observed in 77 (36.3%) of the 212 patients, and spontaneous menarche occurred in 31 patients (14.6%). The frequency of spontaneous breast development was significantly lower in patients with the 45,X karyotype and significantly higher in patients with a structural abnormality of the second X chromosome. The frequency of spontaneous menarche was significantly higher in patients with mosaicism characterized by X monosomy and a cellular line with no structural abnormality of the X chromosome. No significant differences in frequencies of spontaneous breast development and spontaneous menarche were observed between the two dose groups, indicating that GH treatment does not increase the frequency of spontaneous puberty.