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Biomedical subjects

M I New

Publications and source records attributed to M I New.

At least 55 records · Page 3Linked to original sources
PubMed1996

Point mutations abolish 11 beta-hydroxysteroid dehydrogenase type II activity in three families with the congenital syndrome of apparent mineralocorticoid excess.

The 11 beta-hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) converts cortisol into mineralocorticoid receptor inactive cortisone, thus preventing occupation of the non-selective mineralocorticoid receptor by glucocorticoids in the kidney. Mutations generating inactive enzymes have been described in the HSD11B2 gene in the congenital syndrome of apparent mineralocorticoid excess (AME), although proof of mutant protein synthesis was not provided. In the present study we have examined the metabolism of cortisol in mammalian cells transfected with plasmids expressing the wild type and mutant enzymes from three additional families of patients with mutations in the HSD11B2 gene. These studies revealed that the mutants were enzymatically inactive in intact mammalian cells expressing significant levels of both full length and truncated proteins. This is the first study to definitively show that point mutations in the HSD11B2 gene abolish 11 beta HSD2 enzymatic activity in the syndrome of AME.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

Gender change from female to male in classical congenital adrenal hyperplasia.

The psychoendocrinology of the development of normal gender identity and its variations is poorly understood. Studies of gender development in individuals born with endocrinologically well-characterized intersex conditions are heuristically valuable for the disaggregation of factors that are acting in concert during normal development. Four 46,XX individuals with classical congenital adrenal hyperplasia (CAH) and atypical gender identity entered a comprehensive research protocol including systematic interviews and self-report inventories on gender role behavior and identity, sexual history, and psychiatric history. Some of the data on gender variables were compared to data from 12 CAH women with the salt-wasting variant (CAH-SW) with female gender identity. The four patients (ages 28, 35, 38, and 30 years) represented three different subtypes of classical early-onset CAH: 21-OH deficiency, simple virilizing (CAH-SV); 21-OH deficiency, salt-wasting (CAH-SW); and 11-beta-OH deficiency. Their medical histories were characterized by delay beyond infancy or lack of surgical feminization of the external genitalia and progressive virilization with inconsistent or absent glucocorticoid replacement therapy. Although three patients had undergone one or more genital surgeries, all had retained at least some orgasmic capacity. In regard to childhood gender-role behavior, the four gender-change patients tended to be more masculine or less feminine than (behaviorally masculinized) CAH-SW controls. All patients were sexually attracted to females only. The process of gender change was gradual and extended well into adulthood. The most plausible factors contributing to cross-gender identity development in these patients appeared to be neither a particular genotype or endocrinotype nor a sex-typing bias on the part of the parents but a combination of a gender-atypical behavioral self-image, a gender-atypical body image, and the development of erotic attraction to women. Implications for psychosocial management are also discussed.

Adrenal Hyperplasia, Congenital↗
PubMed1996

Dehydroepiandrosterone in morbidly obese adolescents: effects on weight, body composition, lipids, and insulin resistance.

The hormone dehydroepiandrosterone (DHEA) has been reported to have beneficial effects on obesity, diabetes mellitus, and serum lipids in animal studies, but results in human studies are less clear. We conducted a randomized double-blind placebo-controlled trial to determine the effects of DHEA treatment on obesity and related physiologic conditions in adolescents and young adults. In this 10-week study, 13 morbidly obese subjects received a placebo for 2 weeks. After this run-in period, patients were randomized, with seven subjects (mean age, 15.5 years; body mass index [BMI, derived by dividing body weight in kilograms by height in meters squared], 48.2 +/- 9.7 [mean +/- SD]) receiving DHEA 40 mg sublingually twice daily for 8 weeks and six subjects (mean age, 18.0 years; BMI, 52.9 +/- 14) receiving placebo. Variables measured included body weight, body composition, resting metabolic rate (RMR), serum lipid levels, insulin sensitivity, and serum steroid levels. Treatment with DHEA resulted in a statistically significant increase in plasma DHEA and DHEA sulfate (DHEAS) concentrations (P < .01). Testosterone (T) levels were significantly increased in females who received DHEA. DHEA administration had no effect on body weight, sense of well-being, or any other measured variables. These findings suggest that DHEA 40 mg administered sublingually twice daily for 8 weeks has no positive effect on body weight, body composition, serum lipids, or insulin sensitivity in extremely obese adolescents and young adults.

Adolescent↗
PubMed1996

Molecular genetics and pathophysiology of 17 beta-hydroxysteroid dehydrogenase 3 deficiency.

Autosomal recessive mutations in the 17 beta-hydroxysteroid dehydrogenase 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with female external genitalia. Such individuals are usually raised as females, but virilize at the time of expected puberty as the result of increases in serum testosterone. Here we describe mutations in 12 additional subjects/families with this disorder. The 14 mutations characterized to date include 10 missense mutations, 3 splice junction abnormalities, and 1 small deletion that results in a frame shift. Three of these mutations have occurred in more than 1 family. Complementary DNAs incorporating 9 of the 10 missense mutations have been constructed and expressed in reporter cells; 8 of the 9 missense mutations cause almost complete loss of enzymatic activity. In 2 subjects with loss of function, missense mutations testosterone levels in testicular venous blood were very low. Considered together, these findings strongly suggest that the common mechanism for testosterone formation in postpubertal subjects with this disorder is the conversion of circulating androstenedione to testosterone by one or more of the unaffected 17 beta-hydroxysteroid dehydrogenase isoenzymes.

17-Hydroxysteroid Dehydrogenases↗
PubMed1996

Mothers' reactions to prenatal diagnostic procedures and dexamethasone treatment of congenital adrenal hyperplasia.

A retrospective survey of mothers' attitudes toward and experiences of chorionic villus sampling, amniocentesis and dexamethasone (DEX) treatment was conducted in 38 women who underwent a prenatal diagnostic procedure for congenital adrenal hyperplasia because of a previously affected child (n = 37) or because the mother herself was affected (n = 1). Both diagnostic procedures were well tolerated and almost every woman said that the anxiety or discomfort associated with the procedure was far outweighed by the value of knowing whether or not her fetus was affected. The earlier diagnostic information provided by chorionic villus sampling was highly valued. Maternal side-effects of DEX were common (75%) and more than one-third of the women rated one or more side-effects as "severe' (weight gain, fatigue, stomach pain, irritability, facial hair growth). Many women expressed anxiety about possible short- and long-term side-effects of DEX on their unborn children and themselves but all said they would undergo DEX treatment again to prevent virilization.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Steroid 21-hydroxylase deficiency (congenital adrenal hyperplasia).

Congenital adrenal hyperplasia, caused by any one of a number of inborn errors of steroidogenesis in which cortisol is not sufficiently produced by the adrenal cortex, is in most cases due to a deficiency of the enzyme steroid 21-hydroxylase. Classic 21-hydroxylase deficiency occurs in about 1 in 14,000 live births. In classic 21-hydroxylase deficiency, the most common cause of genital ambiguity in females, prenatal exposure to excess androgens results in virilization of the female fetus. Newborn males have normal genitalia. Postnatally, untreated females as well as males present with signs of androgen excess. Three fourths of classic 21-hydroxylase deficiency cases do not effectively synthesize aldosterone and are salt-wasting, a condition that is potentially fatal. An allelic variant of classic 21-hydroxylase deficiency, termed nonclassic 21-hydroxylase deficiency, is associated with a milder enzymatic defect and no genital ambiguity at birth, but postnatal virilization may be seen. The 21-hydroxylase enzyme, a cytochrome P450 hemeprotein (cytochrome P450c21), is encoded by the gene CYP21, which has a closely neighboring homologous pseudogene, CYP21P. Mutations in the CYP21 gene, causing 21-hydroxylase deficiency, are common and occur owing to two mechanisms: gene deletion and apparent gene conversion. Prenatal diagnosis is important to identify a fetus affected with 21-hydroxylase deficiency. Genital ambiguity in affected females can be prevented by proper administration of dexamethasone to the pregnant mother. Postnatally, the treatment of 21-hydroxylase deficiency is lifelong hormonal replacement. With carefully supervised medical treatment, congenital adrenal hyperplasia patients have the capacity for normal puberty and fertility.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Effects of early prenatal dexamethasone on the cognitive and behavioral development of young children: results of a pilot study.

The effect of early prenatal dexamethasone (DEX) exposure on cognitive and behavioral development, behavior problems, and temperament were examined in 26 consecutively identified children aged 6 mo to 5 1/2 years, whose mothers had been DEX-treated during pregnancy because their offspring was at risk for congenital adrenal hyperplasia (CAH), and compared with 14 children from untreated CAH-risk pregnancies. Three children in each group were CAH-affected. Assessments were performed by way of mother-completed standard questionnaires. No significant differences in cognitive abilities or behavior problems were identified. On temperament questionnaires, DEX-exposed children showed more Shyness (p < .004), greater Emotionality (p < .03), less Sociability (p < .04), and a trend for greater Avoiddance (p < .07) than unexposed children. DEX-exposed children also had significantly higher Internalizing (p < .002) and Total Problem scores (p < .05) on the behavior problem measure for 2-3 year olds. The results should be considered preliminary until they have been replicated by the study of a larger sample and direct examination of the children.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Molecular basis of human 3 beta-hydroxysteroid dehydrogenase deficiency.

The enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) catalyses an essential step in the biosynthesis of all classes of steroid hormones. Classical 3 beta-HSD deficiency is responsible for CAHII, a severe form of congenital adrenal hyperplasia (CAH) that impairs steroidogenesis in both the adrenals and gonads. Newborns affected by 3 beta-HSD deficiency exhibit signs and symptoms of adrenal insufficiency of varying degrees associated with pseudohermaphroditism in males, whereas females exhibit normal sexual differentiation or mild virilization. Elevated ratios of 5-ene-to 4-ene-steroids appear as the best biological parameter for the diagnosis of 3 beta-HSD deficiency. The nonclassical form has been suggested to be related to an allelic variant of the classical form of 3 beta-HSD as described for steroid 21-hydroxylase deficiency. To elucidate the molecular basis of the classical form of 3 beta-HSD deficiency, we have analysed the structure of the highly homologous type I and II 3 beta-HSD genes in 12 male pseudohermaphrodite 3 beta-HSD deficient patients as well as in four female patients. The 14 different point mutations characterized were all detected in the type II 3 beta-HSD gene, which is the gene predominantly expressed in the adrenals and gonads, while no mutation was detected in the type I 3 beta-HSD gene predominantly expressed in the placenta and peripheral tissues. The finding of a normal type I 3 beta-HSD gene provides the explanation for the intact peripheral intracrine steroidogenesis in these patients and increased androgen manifestations at puberty. The influence of the detected mutations on enzymatic activity was assessed by in vitro expression analysis of mutant enzymes generated by site-directed mutagenesis in COS-1 cells. The mutant type II 3 beta-HSD enzymes carrying mutations detected in patients affected by the salt-losing form exhibit no detectable activity in intact transfected cells, whereas those with mutations found in nonsalt-loser index cases have some residual activity ranging from approximately 1-10% compared to the wild-type enzyme. Although in general, our findings provide a molecular explanation for the enzymatic heterogeneity ranging from the severe salt-losing form to the clinically inapparent salt-wasting form of the disease, we have observed that the mutant L108W or P186L enzymes found in a compound heterozygote male presenting the salt-wasting form of the disease, has some residual activity (approximately 1%) similar to that observed for the mutant N100S enzyme detected in a homozygous male patient suffering from a nonsalt-losing form of this disorder.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

Failure of steroid replacement to consistently normalize pituitary function in congenital adrenal hyperplasia: hormonal and MRI data.

Exogenous glucocorticoid replacement in patients with congenital adrenal hyperplasia (CAH), who due to an adrenal 21-hydroxylase enzyme deficiency are unable to produce endogenous glucocorticoids, is aimed at normalizing hypothalamic-pituitary-adrenal function. Excess androgen production by the adrenals is thus decreased. Despite standard glucocorticoid replacement doses (12.5-40 mg, 10.5-27 mg/m2/day hydrocortisone equivalents) 4 of 7 patients ranging in age from 14 to 33 years had abnormalities of the pituitary on MRI. Three appeared to have microadenomas and 1 had an empty sella. Five (3 salt wasters, 2 simple virilizers) of these 7 patients had 60-min p.m. ovine corticotropin-releasing hormone (oCRH) stimulation studies. The mean (logarithm) area under the ACTH curve for 0-60 min after oCRH stimulation was significantly greater in patients than controls (p < 0.0001). Mean ACTH at each time point before and after oCRH stimulation was similarly greater in patients than controls (p < 0.05). Two of these patients had pituitary microadenomas, 1 had an empty sella; all 3 were salt wasters. Despite standard glucocorticoid replacement, adolescent and young adult patients with CAH tend to have high basal ACTH and ACTH hyperresponsiveness to oCRH, as well as structural abnormalities of the pituitary. The inevitable periods of under- and overexposure to glucocorticoids in CAH patients may over time cause abnormalities of the hypothalamic-pituitary-adrenal axis.

17-alpha-Hydroxyprogesterone↗
PubMed1995

The R337C mutation generates a high Km 11 beta-hydroxysteroid dehydrogenase type II enzyme in a family with apparent mineralocorticoid excess.

The 11 beta-hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) inactivates glucocorticoids in the kidney and thus permits aldosterone to occupy the non-selective mineralocorticoid receptor in epithelial tissues. We have recently described a C to T transition in the HSD11B2 gene which results in an arginine to cysteine mutation (R337C) in the 11 beta HSD2 enzyme in a consanguineous family with three siblings suffering from Apparent Mineralocorticoid Excess (AME). In the present study we have examined the metabolism of cortisol in mammalian cells transfected with plasmids expressing the wild type and mutant enzymes. In whole cells the Km of the normal enzyme was 110nM, while the enzyme containing the R337C mutation displayed a Km of 1010nM. Further experiments revealed that the mutant was totally inactive in cell free preparations, suggesting that it has additional properties which may compromise its activity in whole cells.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1995

Rapid deoxyribonucleic acid analysis by allele-specific polymerase chain reaction for detection of mutations in the steroid 21-hydroxylase gene.

Rapid DNA analysis based on allele-specific polymerase chain reaction (PCR) using mutation site-specific primers was developed to detect mutations in the CYP21 gene known to cause steroid 21-hydroxylase deficiency. In contrast to the previous method, in which PCR of genomic DNA was followed by dot blot analysis with radioactive probes and multiple rounds of stripping and reprobing for each of the 8 most common mutation sites, the results using this new method were immediately visualized after the PCR run by ethidium bromide-stained agarose gel electrophoresis. Using allele-specific PCR, mutation(s) were identified on 148 affected chromosomes out of 160 tested. Although mutation(s) were identified on only one chromosome of 11 of these patients, their parents showed a consistent pattern on DNA analysis. The only exception was that in one family, in which the parents each had a detectable mutation, a mutation was detected on only one allele of the patient. Most likely there is a mutation in the patient's other allele that could have arisen de novo or was inherited from the parent and was not evident in the transmitting parent's phenotype. When compared with the dot blot procedure, allele-specific PCR is more rapid, less labor-intensive, and avoids the use of radioactivity.

Alleles↗
PubMed1995

Prenatal treatment and diagnosis of congenital adrenal hyperplasia owing to steroid 21-hydroxylase deficiency.

Since 1986, prenatal diagnosis and treatment of congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21-OHD) have been carried out in 239 pregnancies. In 145, diagnoses were made by amniocentesis, whereas 77 were diagnosed using chorionic villus sampling. A newly developed, rapid allele-specific polymerase chain reaction was used for DNA analysis in some cases. Of 239 pregnancies evaluated, 37 babies were affected with classical 21-OHD. Of these, 21 were females, 13 of whom were treated prenatally with dexamethasone. Dexamethasone administered at or before 10 weeks gestation (9 affected female fetuses) was effective in reducing virilization. Seven fetuses had affected female siblings (Prader stages 1-5); 3 of these were born with entirely normal female genitalia, whereas the other 4 were significantly less virilized (Prader stages 1-2) than their siblings. The remaining 2 newborns had male siblings; 1 was born with normal genitalia, and the other was Prader stage 1. No significant or enduring side-effects were noted in either the mothers or the fetuses, indicating that dexamethasone treatment is safe. Prenatally treated newborns did not differ in weight, length, or head circumference from untreated unaffected newborns. Based on our experience, proper prenatal diagnosis and treatment of 21-OHD is effective in significantly reducing or eliminating virilization in the affected female. This spares the newborn female the consequences of genital ambiguity, i.e. genital surgery, sex misassignment, and gender confusion.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Steroid 21-hydroxylase deficiency: genotype may not predict phenotype.

Steroid 21-hydroxylase deficiency is the most frequent cause of congenital adrenal hyperplasia. We have determined the 21-hydroxylase genotype in 197 patients with congenital adrenal hyperplasia owing to 21-hydroxylase deficiency and assessed phenotypic characteristics based on 1) genital status with respect to virilization in females, 2) ACTH stimulation tests to evaluate the secretion of androgens and 17-hydroxyprogesterone, and 3) salt deprivation tests to precisely describe the phenotype with respect to aldosterone deficiency and salt wasting. After dividing our patients into 26 21-hydroxylase gene mutation-identical groups, we found that, in general, the patient's phenotype matched the severity of the genotype. However, in 13 of these groups, the genotype did not always predict the phenotype, even within families. This study, has demonstrated that the 10 most common mutations observed in the 21-hydroxylase gene result in phenotypes that are not always concordant with the genotype.

Adrenal Hyperplasia, Congenital↗