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Apparent mineralocorticoid excess is a recessively inherited hypertensive syndrome caused by mutations in the 11beta-hydroxysteroid dehydrogenase type 2 gene, which encodes the enzyme normally responsible for converting cortisol to inactive cortisone. Failure to convert cortisol to cortisone in mineralocorticoid-sensitive tissues permits cortisol to bind to and activate mineralocorticoid receptors, causing hypervolemic hypertension. Typically, these patients have increased ratios of cortisol to cortisone and of 5alpha- to 5beta-cortisol metabolites in serum and urine. We have studied 3 patients in 2 families with severe, apparent mineralocorticoid excess and other family members in terms of their genetic, biochemical, and clinical parameters, as well as normal controls. Two brothers were homozygous for an A328V mutation and the third patient was homozygous for an R213C mutation in the 11beta-hydroxysteroid dehydrogenase type 2 gene; both mutations caused a marked reduction in the activity of the encoded enzymes in transfection assays. The steroid profiles of the 7 heterozygotes and 2 other family members studied were completely normal. The results of a novel assay used to distinguish 5alpha- and 5beta-tetrahydrometabolites suggest that 5beta-reductase activity is reduced or inhibited in apparent mineralocorticoid excess. In 1 patient undergoing renal dialysis for chronic renal insufficiency, direct control of salt and water balance completely corrected the hypertension, emphasizing the importance of mineralocorticoid action in this syndrome.

We evaluated the involvement of a possible dysfunction of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in the fetal growth retardation and poor growth rates of children born with intrauterine growth retardation (IUGR). Children with IUGR have a nephron deficit and are also at risk of developing cardiovascular diseases, high blood pressure, glucose intolerance, and dyslipidemia later in life. The major site of 11beta-HSD2 production is the kidney and its deficit causes hypertension. We investigated plasma concentrations of cortisol (F) and cortisone (E) and the F/E ratio in 26 control children and in 40 IUGR children without catch-up growth. We also determined cholesterol, HbA1C, insulin, and glucose levels in plasma. Mean F values were 106 +/- 54.2 ng/mL in control children and 114.6 +/- 53.2 ng/mL in IUGR children. Mean E values were 19.5 +/- 7.1 ng/mL in control children and 17.9 +/- 6.85 ng/mL in IUGR children. The mean F/E ratio for control children was 5.5 +/- 1.7. Eight (20%) of the IUGR children (IUGR children of group 1) had high F/E ratios more than 2 SD above the normal mean: 13.15 +/- 4.26, (p < 0.0001) as compared to control children, whereas the other 32 children (IUGR children of group 2) had normal F/E ratios: 5.40 +/- 1.43 (p = 0.68). Childhood height was significantly lower for group 1 than group 2 children (-3.63 SD and -2.92 SD, respectively: p < 0.01) and was negatively correlated with the F/E ratio (p < 0.01). Systolic blood pressure was higher for group 1 (p = 0.005) and for group 2 (p = 0.015) than for control children. The diastolic pressure in IUGR children of group 1 was higher than that in control children (p = 0.013) and slightly higher than that in group 2 (p = 0.1, ns). Cholesterol concentrations were higher in group 1 than in group 2 (p = 0.029), and controls (p = 0.017) and correlated positively with F/E (0.02 < p < 0.05). Fasting insulin concentrations were higher in group 1 than in group 2 (ns) and controls (ns). There was no difference in mean fasting glucose concentrations, or HbA1C between the three groups. Twenty percent of our children with IUGR and poor growth rates had high F/E ratios, suggesting a possible partial 11beta-HSD2 deficit. Whether these children are at high risk of developing cardiovascular diseases as adults remains to be further evaluated.

The adipocyte-specific hormone leptin, the product of the obese (ob) gene, regulates adipose-tissue mass through hypothalamic effects on satiety and energy expenditure. Leptin acts through the leptin receptor, a single-transmembrane-domain receptor of the cytokine-receptor family. In rodents, homozygous mutations in genes encoding leptin or the leptin receptor cause early-onset morbid obesity, hyperphagia and reduced energy expenditure. These rodents also show hypercortisolaemia, alterations in glucose homeostasis, dyslipidaemia, and infertility due to hypogonadotropic hypogonadisms. In humans, leptin deficiency due to a mutation in the leptin gene is associated with early-onset obesity. Here we describe a homozygous mutation in the human leptin receptor gene that results in a truncated leptin receptor lacking both the transmembrane and the intracellular domains. In addition to their early-onset morbid obesity, patients homozygous for this mutation have no pubertal development and their secretion of growth hormone and thyrotropin is reduced. These results indicate that leptin is an important physiological regulator of several endocrine functions in humans.

We have developed a new assay for cortisone (E) in serum, saliva, and urine involving Celite chromatography followed by RIA with 125I-labeled E and scintillation proximity assay. The chromatography step separates cortisol (F) from E, and in combination with their RIAs, permits assessment of the status of the F-E shuttle. We report the results of basal, postcorticotropin (ACTH), and postdexamethasone E and F concentrations and their circadian fluctuations in the serum, saliva, and urine of healthy volunteers. The serum and urine F/E ratios were increased in patients with ectopic ACTH secretion, whereas in adrenal adenoma and Cushing disease only the urinary ratio was increased. In chronic renal insufficiency this ratio was increased in serum (23.5 +/- 3.9) but diminished in saliva (0.38 +/- 0.11), and in apparent mineralocorticoid excess the ratios were high in serum (44.3 +/- 9.3) and urine (5.35 +/- 0.85) compared with those of healthy subjects (serum 9.8 +/- 3.5, urine 0.52 +/- 0.29, saliva 0.52 +/- 0.29).

We have performed clinical, in vitro biochemical, and genetic studies of a patient with severe insulin resistance, considerable growth restriction, and Rabson-Mendenhall syndrome (patient RM-3). The blood IGF-I level was undetectable in this patient, although the GH level was moderately decreased. During the postprandial period, glycemia, ketonuria, and plasma glucagon were very elevated despite high doses of exogenous insulin (glucose levels up to 30 mmol/L). In the postabsorptive state, blood glucose was normalized with small amounts of insulin; ketonuria, and glucagon levels were reduced but remained supranormal. Erythrocytes and cultured skin fibroblasts from the patient displayed a decrease in cell surface insulin receptors (IRs). The ability of physiologic concentrations of insulin to stimulate metabolic processes was altered in patient fibroblasts. Analysis of the IR gene by denaturing gradient gel electrophoresis and direct sequencing showed a homozygous missense mutation in exon 3, replacing Cys284 by Tyr in the alpha-subunit. In conclusion, marked primary insulin resistance was evidenced in patient cells as a result of a structural alteration in the IR alpha-subunit. The in vitro studies could not account alone for the in vivo metabolic alterations because glucose homeostasis varied considerably during the day in the patient.

The IGF-I gene from leukocyte DNA of a control population of normal stature was studied using Southern blotting. Restriction fragment lengths for 21 enzymes were determined and three restriction fragment length polymorphisms (RFLP) were found (EcoRV, HindIII, and PvuII). In addition, the IGF-I gene of 64 constitutionally short subjects, five Pygmies, and 10 constitutionally tall subjects was analyzed. No IGF-I gene alterations were detectable by Southern blot in any of these conditions. Linkage analysis using genetic markers (RFLP) yielded results that were uninformative for five constitutionally short families investigated, owing to the limited number of RFLP and their low incidence (17% for the 5.2-kb HindIII, 5-kb PvuII RFLP alleles, and 13% for the 13-kb EcoRV RFLP allele). The EcoRV RFLP was found to map near Exon 1. The incidence of the 13-kb polymorphic allele with EcoRV proved to be lower (4%) in the group with constitutionally short stature than in controls. These results could suggest that modifications in the region of the IGF-I gene may be involved in constitutionally short subjects.