Subcutaneous and visceral adipose tissue: their relation to the metabolic syndrome.

Methods for assessment, e.g., anthropometric indicators and imaging techniques, of several phenotypes of human obesity, with special reference to abdominal fat content, have been evaluated. The correlation of fat distribution with age, gender, total body fat, energy balance, adipose tissue lipoprotein lipase and lipolytic activity, adipose tissue receptors, and genetic characteristics are discussed. Several secreted or expressed factors in the adipocyte are evaluated in the context of fat tissue localization. The body fat distribution and the metabolic profile in nonobese and obese individuals is discussed relative to lipolysis, antilypolysis and lipogenesis, insulin sensitivity, and glucose, lipid, and protein metabolism. Finally, the endocrine regulation of abdominal visceral fat in comparison with the adipose tissue localized in other areas is presented.

Cardiovascular, metabolic and hormonal responses to the progressive exercise performed to exhaustion in patients with type 2 diabetes treated with metformin or glyburide.

OBJECTIVES: To evaluate the effects of Metformin and Glyburide on cardiovascular, metabolic and hormonal parameters during progressive exercise performed to exhaustion in the post-prandial state in women with type 2 diabetes (T2DM). DESIGN AND METHODS: Ten T2DM patients treated with Metformin (M group), 10 with Glyburide (G group) and 10 age-paired healthy subjects exercised on a bicycle ergometer up to exercise peak. Cardiovascular and blood metabolic and hormonal parameters were measured at times -60 min, 0 min, exercise end, and at 10 and 20 minutes of recovery phase. Thirty minutes before the exercise, a standard breakfast was provided to all participants. The diabetic patients took Metformin or Glyburide before or with meal. RESULTS: Peak oxygen uptake (VO(2)) was lower in patients with diabetes. Plasma glucose levels remained unchanged, but were higher in both diabetic groups. Patients with diabetes also presented lower insulin levels after meals and higher glucagon levels at exercise peak than C group. Serum cortisol levels were higher in G than M group at exercise end and recovery phase. Lactate levels were higher in M than G group at fasting and in C group at exercise peak. Nor epinephrine, GH and FFA responses were similar in all 3 groups. CONCLUSION: Progressive exercise performed to exhaustion, in the post-prandial state did not worsen glucose control during and after exercise. The administration of the usual dose of Glyburide or Metformin to T2DM patients did not influence the cardiovascular, metabolic and hormonal response to exercise.

Relationship between glycemic control and coronary artery disease severity, prevalence and plaque characteristics by computed tomography coronary angiography in asymptomatic type 2 diabetic patients.

Evaluate whether glycemic control in type 2 diabetes (DM2) asymptomatic for coronary artery disease (CAD) affects not only the presence and magnitude of CAD but also the characteristics of plaque vulnerability using multidetector row computed coronary tomography (MDCT). Acute coronary syndrome (ACS) is frequently observed in asymptomatic DM2 patients. Positive vessel remodeling (PR) and low-attenuation plaques (LAP) identified by MDCT have been demonstrated to be characteristics of subsequent culprit lesions of ACS. However, little is known regarding plaque characteristics in asymptomatic diabetic patients and their relationship with glycemic control. Ninety asymptomatic DM2 patients, aged 40-65 years old, underwent MDCT. The presence of atherosclerotic obstruction, defined as coronary stenosis ≥50 %, and plaque characteristics were compared between two groups of patients with A1c < 7 and A1c ≥ 7 %. Of the 90 patients, 38 (42.2 %) presented with coronary atherosclerotic plaques, 11 had A1c < 7 % and 27 had A1c ≥ 7 % (p = 0.0006). Fourteen patients had significant lumen obstruction higher than 50 %: 3 in the A1c < 7 % group and 11 in the A1c ≥ 7 % group (p = 0.02). Non-calcified plaque was more prevalent in the A1c ≥ 7 % group (p = 0.005). In eleven patients, the simultaneous presence of two vulnerability plaque characteristics (PR and LAP) were observed more frequently in the A1c ≥ 7 group (n = 8) than in the A1c < 7 group (n = 3) (p = 0.04). Asymptomatic DM2 patients with A1c ≥ 7 % have a higher frequency of CAD and a higher proportion of vulnerable atherosclerotic coronary plaque by MDCT compared to patients with DM2 with A1c < 7 in our study.

Insulin resistance in Cushing's disease. Evaluation by studies of insulin binding to erythrocytes.

Studies of 125I -insulin binding to erythrocytes (RBC) from 5 patients with Cushing's disease were performed in an attempt to evaluate the insulin resistance in this disease. Five obese, nondiabetic patients and six normal subjects served as controls. Insulin resistance was present in both the obese, nondiabetic subjects and in the patients with Cushing's disease. Patients with Cushing's disease showed insulin resistance out of proportion to obesity, and of greater severity than in the obese subjects. As in previous studies, the insulin resistance of the obese subjects could be at least partially ascribed to a reduced number of receptors. In contrast, in our patients with Cushing's disease, no physiologically significant changes in the parameters of insulin-receptor interaction could be demonstrated. This suggests that the RBC insulin receptor is not involved in this type of insulin resistance.

Sequential studies of glucose tolerance and red blood cell insulin receptors in normal human pregnancy.

Insulin binding to erythrocytes was sequentially studied in 12 healthy pregnant women during the anabolic (11-22 wk) and the catabolic (31-38 wk) gestational phases. For comparison, we studied 12 nonpregnant subjects at mid-luteal and mid-follicular menstrual phases. Oral glucose tolerance tests were also performed during these studies. There was a progressive worsening of the glucose tolerance from the anabolic to the catabolic phase associated with fasting hypoglycemia and hyperinsulinemia. The worsening of glucose tolerance was accompanied by a progressive increment of insulin secretion. Insulin binding to red blood cells increased progressively from the anabolic to the catabolic phase, due to an increased number of receptors per cell, associated with a reduction in the apparent affinity at the low occupancy levels. We concluded that the insulin resistance of pregnancy was not accompanied by an impaired binding of insulin to its receptors, at least in the RBC. The data suggest that the defect of insulin action lies at a site distal to the receptor.

Overnight lowering of free fatty acids with Acipimox improves insulin resistance and glucose tolerance in obese diabetic and nondiabetic subjects.

Obesity is commonly associated with elevated plasma free fatty acid (FFA) levels, as well as with insulin resistance and hyperinsulinemia, two important cardiovascular risk factors. What causes insulin resistance and hyperinsulinemia in obesity remains uncertain. Here, we have tested the hypothesis that FFAs are the link between obesity and insulin resistance/hyperinsulinemia and that, therefore, lowering of chronically elevated plasma FFA levels would improve insulin resistance/hyperinsulinemia and glucose tolerance in obese nondiabetic and diabetic subjects. Acipimox (250 mg), a long-acting antilipolytic drug, or placebo was given overnight (at 7:00 P.M., 1:00 A.M., 7:00 A.M.) to 9 lean control subjects, 13 obese nondiabetic subjects, 10 obese subjects with impaired glucose tolerance, and 11 patients with type 2 diabetes. Euglycemic-hyperinsulinemic clamps and oral glucose tolerance tests (75 g) were performed on separate mornings after overnight Acipimox or placebo treatment. In the three obese study groups, Acipimox lowered fasting levels of plasma FFAs (by 60-70%) and plasma insulin (by approximately 50%). Insulin-stimulated glucose uptake during euglycemic-hyperinsulinemic clamping was more than twofold higher after Acipimox than after placebo. Areas under the glucose and insulin curves during oral glucose tolerance testing were both approximately 30% lower after Acipimox administration than after placebo. We conclude that lowering of elevated plasma FFA levels can reduce insulin resistance/hyperinsulinemia and improve oral glucose tolerance in lean and obese nondiabetic subjects and in obese patients with type 2 diabetes.

Previous exercise attenuates muscle sympathetic activity and increases blood flow during acute euglycemic hyperinsulinemia.

Insulin infusion causes muscle vasodilation, despite the increase in sympathetic nerve activity. In contrast, a single bout of exercise decreases sympathetic activity and increases muscle blood flow during the postexercise period. We tested the hypothesis that muscle sympathetic activity would be lower and muscle vasodilation would be higher during hyperinsulinemia performed after a single bout of dynamic exercise. Twenty-one healthy young men randomly underwent two hyperinsulinemic euglycemic clamps performed after 45 min of seated rest (control) or bicycle exercise (50% of peak oxygen uptake). Muscle sympathetic nerve activity (MSNA, microneurography), forearm blood flow (FBF, plethysmography), blood pressure (BP, oscillometric method), and heart rate (HR, ECG) were measured at baseline (90 min after exercise or seated rest) and during hyperinsulinemic euglycemic clamps. Baseline glucose and insulin concentrations were similar in the exercise and control sessions. Insulin sensitivity was unchanged by previous exercise. During the clamp, insulin levels increased similarly in both sessions. As expected, insulin infusion increased MSNA, FBF, BP, and HR in both sessions (23 +/- 1 vs. 36 +/- 2 bursts/min, 1.8 +/- 0.1 vs. 2.2 +/- 0.2 ml.min(-1).100 ml(-1), 89 +/- 2 vs. 92 +/- 2 mmHg, and 58 +/- 1 vs. 62 +/- 1 beats/min, respectively, P < 0.05). BP and HR were similar between sessions. However, MSNA was significantly lower (27 +/- 2 vs. 31 +/- 2 bursts/min), and FBF was significantly higher (2.2 +/- 0.2 vs. 1.8 +/- 0.1 ml.min(-1).100 ml(-1), P < 0.05) in the exercise session compared with the control session. In conclusion, in healthy men, a prolonged bout of dynamic exercise decreases MSNA and increases FBF. These effects persist during acute hyperinsulinemia performed after exercise.

Metabolic effects of dietary sucrose and fructose in type II diabetic subjects.

OBJECTIVE: To investigate the metabolic effects of dietary fructose and sucrose in type II diabetic patients. RESEARCH DESIGN AND METHODS: Sixteen well-controlled type II diabetic subjects were fed three isocaloric diets for 28 days each. The three diets provided 50-55, 15, and 30-35% of total energy from carbohydrate, protein, and fat, respectively. In one diet, 20% of total calories were derived from fructose; in another, 19% of total calories were derived from sucrose; and in the control diet, only 5% of daily calories were derived from sugars, all other carbohydrates being supplied as polysaccharides. RESULTS: No significant differences were observed between either the fructose or the sucrose diet and the control polysaccharide diet in any of the measures of glycemic control, serum lipid levels, or insulin and C-peptide secretion. CONCLUSIONS: Our data suggest that in the short and middle terms, high fructose and sucrose diets do not adversely affect glycemia, lipemia, or insulin and C-peptide secretion in well-controlled type II diabetic subjects.

Ultrasonographic abnormalities of the pancreas in IDDM and NIDDM patients.

OBJECTIVE: To evaluate the relationship between the type and duration of diabetes and pancreas size by ultrasonography. RESEARCH DESIGN AND METHODS: Pancreas images of 40 IDDM and 36 NIDDM patients with 0.3-34 yr of disease were compared with those of 60 normal healthy control subjects. RESULTS: The diameters +/- SD of the head, body, and tail of the pancreas in IDDM patients (1.9 +/- 0.3; 0.9 +/- 0.2; and 1.4 +/- 0.2 cm, respectively) were smaller than in NIDDM patients (2.7 +/- 0.4; 1.2 +/- 0.3; and 1.8 +/- 0.4 cm, respectively) and control group subjects (2.4 +/- 0.4; 1.1 +/- 0.3; and 1.8 +/- 0.4 cm, respectively). The pancreatic shrinkage in IDDM patients was clearly evident after 10 yr of the disease. NIDDM patients and control subjects had similar pancreatic dimensions, except for a greater body thickness in NIDDM patients with > 10 yr of disease (1.2 +/- 0.4 vs. 1.1 +/- 0.3 cm). These results were not related to differences in age, sex, and body size. Pancreas image was hypoechogenic in 72.5% of IDDM patients and hyperechogenic in 83.3% of NIDDM patients. CONCLUSIONS: Smaller pancreases in IDDM patients in comparison with NIDDM patients and control subjects were clearly demonstrated only after 10 yr of disease. Patients with NIDDM were not affected by pancreatic dimensions, except for a greater body thickness after 10 yr of disease. Pancreatic echogenicity increased with age.

Periodic remission in Cushing's disease with paradoxical dexamethasone response: an expression of periodic hormonogenesis.

A patient with Cushing's disease due to a chromophobe adenoma was studied for 243 days before pituitary surgery and evidence for periodicity in cortisol steroid production was found with cycles occurring every 85.8 days (peak-to-peak length), associated with laboratory remissions and paradoxical response to dexamethasone. The autonomy of ACTH secretion was suggested by the nonresponsiveness to repeated lysine-vasopressin stimulation tests and lack of increase in urinary 170HCS following metyrapone. A distinct response of the hyperplastic glands (as demonstrated by percutaneous adrenal venography) was obtained on several B1-24 corticotropin stimulation. The patient's hypercortisolism disappeared following removal of the chromophobe adenoma through transphenoidal hypophysectomy.

Hyposialylated thyroglobulin in a patient with congenital goiter and hypothyroidism.

A large family (14 children) with congenital goiter whose parents are first cousins was studied. Thyroid tissue was obtained, after 125I in vivo labeling, from one of the siblings (JBM). Gel filtration of thyroid proteins indicated that thyroglobulin (Tg) eluted as a single symmetrical peak in the same position as authentic 19S Tg. Gel electrophoresis in a 7.5% sodium dodecyl sulfate-polyacrylamide gel revealed a major band with the same mobility and immunoreactivity as normal 19S Tg. Hydrolysis of the patient's Tg indicated that most of the radioactivity was mono- and diiodotyrosines. The yield of T4 from JBM Tg (26 pmol/mg protein) was 5-fold less than normal thyroid tissue (140 pmol/mg protein) and approximately half of that in thyroid tissue from endemic goiter (51 pmol/mg). Total T3 released from JBM Tg was similar to the other two tissues. When the carbohydrate content of normal and patient Tg was analyzed, there was no differences in glucosamine, galactose or mannose content. However, unlike normal and endemic-goiter Tg, that had a mean sialic acid content of 7.3 and 5.6 micrograms/mg protein, respectively, the sialic acid concentration of the patients Tg was only 0.3 microgram/mg. Sialyltransferase activity was readily demonstrated in homogenate from normal thyroid or endemic goiter, but no sialyltransferase activity was detectable in a homogenate of JBM-thyroid tissue. We conclude that the finding of severely hyposialylated Tg is linked to a defect in iodotyrosine coupling seen in this patient with a possibly abnormal migration of Tg into the follicular lumen.

Contrast analysis for the evaluation of the circadian rhythms of plasma cortisol, androstenedione, and testosterone in normal men and the possible influence of meals.

To evaluate the circadian rhythms of plasma androstenedione (delta) and testosterone (T), we used continuous blood withdrawal at 30-min intervals for 24 h to obtain integrated concentrations in six normal men. The data were submitted to contrast analysis as well as to a graphical method with smoothing of the variations between samples. As reference, cortisol (F) levels also were measured, since they have a well defined circadian rhythm. Integrated F concentrations had a circadian rhythm, with the highest levels between 0500 and 0900 h, nadir values between 2000 and 300 h, and secretory peaks coincident with lunch and dinner hours, suggesting the influence of food ingestion on secretion. Integrated androstenedione concentrations also had a circadian rhythm, with the highest levels between 0530 and 0930 h and the lowest between 1900 and 0230 h. There also were peaks with lunch and dinner, however, occurring some minutes before the corresponding ones for F. Integrated T concentrations had a circadian rhythm, with the peak values between 0100 and 1130 h and the lowest levels between 0700 and 2100 h. There were no peaks of the T integrated concentrations during the meal periods as found with F and delta. Furthermore, no correlation was found between the integrated concentrations of T and F or delta.

Atypical antiinsulin receptor antibodies in a patient with type B insulin resistance and scleroderma.

We studied a 23-yr-old woman with scleroderma and type B insulin resistance. The association with autoimmune disease suggested that the insulin resistance resulted from autoantibodies to the insulin receptor. However, in preliminary studies, serum antireceptor antibodies were not detected in an assay that measures the ability of the antibodies to inhibit insulin binding to the insulin receptor. Antireceptor antibodies were subsequently detected by their ability to immunoprecipitate affinity-labeled receptors. After the patient had received immunosuppressive therapy with prednisone and cyclophosphamide for 3 months, her insulin resistance remitted, and she developed hypoglycemia. Simultaneously with the remission of insulin resistance, the titer of serum antireceptor antibody (measured by the immunoprecipitation assay) fell to less than 1% of the previous level. In a series of 21 patients, this is the first patient with antireceptor antibodies that bound to the insulin receptor without inhibiting insulin binding.

A nonsense mutation causes human hereditary congenital goiter with preferential production of a 171-nucleotide-deleted thyroglobulin ribonucleic acid messenger.

Defective or impaired thyroglobulin (Tg) synthesis usually results in congenital goitrous hypothyroidism, virtual absence of Tg in thyroid tissue, and the presence of an elevated concentration of iodoalbumin. The final result of these abnormalities is a decreased rate of T3 and T4 synthesis. We have previously reported two siblings with this syndrome that was attributable to decreased levels of thyroid tissue Tg mRNA, resulting in decreased translation of a fully mature Tg. Further molecular studies in this family are the subject of this report. The Tg mRNA from normal and goitrous thyroid tissue was first reverse transcribed and divided into five overlapping portions from positions 57-8448, and the resulting cDNAs were amplified by polymerase chain reaction and analyzed by agarose gel electrophoresis. The amplification of nucleotides (nt) 4502-5184 from control thyroid tissue Tg mRNA showed a predominant fragment of 683 basepairs (bp) and a minor fragment of 512 bp. This latter fragment contained a 171-nt deletion that mapped between positions 4567 and 4737 of the Tg mRNA. In contrast, the fragment predominantly present in the congenital goiter was 512 bp. The sequencing of the 683-bp fragment revealed that the responsible mutation is a cytosine to thymine transition, creating a stop codon at position 1510. This results in loss of a TaqI restriction site. The point mutation is, thus, removed from a portion of the transcripts by the preferential accumulation in the goiter of a 171-nt-deleted Tg mRNA. The reading frame is maintained and is potentially fully translatable into a Tg polypeptide chain shorter by 57 residues. The presence of the deleted Tg mRNA in normal thyroid tissue, albeit at a low level, strongly suggests that the deleted mRNA sequence corresponds to a complete exon. Our studies suggest that the shorter, alternatively spliced Tg mRNA predominates in the goitrous tissue and probably has a shorter half-life. This would explain the tissue's low Tg mRNA levels, previously reported. Moreover, translation of the mutated transcript would generate a severely truncated Tg polypeptide with limited ability to generate thyroid hormone, resulting in congenital goitrous hypothyroidism.

Estimation of body fat and lean tissue distribution by dual energy X-ray absorptiometry and abdominal body fat evaluation by computed tomography in Cushing's disease.

Body composition determined by dual energy x-ray absorptiometry and the abdominal visceral fat component determined by computed tomographic scanning were examined in women with Cushing's disease and compared with those in obese women with the same anthropometric parameters and those in nonobese women. Patients with Cushing's had no increase in total body fat or the trunk region (android) component, but had a higher intraabdominal fat area compared to the obese subjects. The total lean tissue mass was slightly reduced in Cushing's compared to that in the obese subjects due to a significant decrease in the muscle of the legs and arms; the reduced amounts of fat and lean tissue masses in the arms were the most significant findings in hypercortisolism. The body mineral and bone calcium contents were slightly reduced in Cushing's compared to those in the obese controls. Thus, although obese subjects had more fat and lean tissue and mineral masses than their normal weight counterparts, the Cushing's patients, with the same total fat mass and its components (except in the arms) as obese individuals, present total lean tissue and fractions, including body mineral and bone calcium contents, similar to those in nonobese subjects due to the depletion of the protein depots, as seen in hypercortisolism.

The zonal origins of the mineralocorticoid hormones in the 21-hydroxylation deficiency of congenital adrenal hyperplasia.

The 0800 h plasma concentrations of the mineralocorticoid hormones, 18-hydroxydeoxycorticosterone (18-OHDOC), deoxycorticosterone (DOC), corticosterone, 18-hydroxycorticosterone (18-OHB), and aldosterone, in six patients with nonsalt-losing congenital adrenal hyperplasia revealed two groupings of these steroids: in one group, DOC, 18-OHB, and aldosterone were significantly elevated (P less than 0.001) at 51.7 +/- 18.0, 70.8 +/- 14.2, and 22.7 +/- 3.0 ng/dl, respectively; in the other group, corticosterone and 18-OHDOC were normal at 363.6 +/- 76.0 and 7.8 +/- 1.1 ng/dl, respectively. No significant increases in response to upright posture were observed in DOC, 18-OHB, or aldosterone. After a 1-h Cortrosyn stimulation test, the already elevated levels of DOC, 18-OHB, and aldosterone showed slight additional increases, but the normal levels of corticosterone and 18-OHDOC changed little within the normal unstimulated range. In these patients certain mineralocorticoid hormone patterns permit the identification of the zonal origins of steroids. The normal and fixed levels of 18-OHDOC and corticosterone, zona fasciculata steroids, are similar to those of cortisol and imply deficiency of formation and of their precursor, zona fasciculata DOC, a 21-hydroxylated steroid. Both the mineralocorticoid and glucocorticoid pathways distal to 21-hydroxylation are impaired in the zona fasciculata. However, the elevated and partially responsive levels of DOC, 18-OHB, and aldosterone imply that there is greater activation of 21-hydroxylation in the zona glomerulosa than in the zona fasciculata, with its normal fixed steroid levels, and that the elevated level of DOC is primarily from this zone.

Determination of the source(s) of androgen overproduction in hirsutism associated with polycystic ovary syndrome by simultaneous adrenal and ovarian venous catheterization. Comparison with the dexamethasone suppression test.

To determine the source(s) of the excessive androgen production in patients with the polycystic ovary syndrome (PCOS), 12 hirsute women with PCOS underwent selective left adrenal and left ovarian venous catheterization. Blood samples were collected simultaneously for determination of cortisol, 17-hydroxy-progesterone, androstenedione (delta), testosterone (T), dehydroepiandrosterone, and dehydroepiandrosterone sulfate. The relative contributions of adrenal secretion rates of T and delta in each patient were estimated by relating their adrenal gradients to those of cortisol. From such calculations we found that in all patients the major source of androgens was the ovary (direct ovarian secretion and/or ovarian secretion of prehormones which then were converted to androgen in the peripheral circulation). After catheterization, 11 of the 12 patients underwent a 5-day dexamethasone suppression test (2 mg/day). In 7 patients studied, plasma delta and/or T levels decreased significantly. Our results indicate that in hirsutism associated with the PCOS, the predominant source of androgens is the ovaries and that glucocorticoid suppression cannot assign adrenal origin as the site of excessive androgens.

A 138-nucleotide deletion in the thyroglobulin ribonucleic acid messenger in a congenital goiter with defective thyroglobulin synthesis.

Two siblings (HSN and AcSN) with congenital goitrous hypothyroidism were investigated in terms of clinical, biochemical, and molecular biology. Diagnosis of defective thyroglobulin (Tg) was based on findings of low serum T4, low normal or normal serum T3, a negative percholate discharge test, and the virtual absence of the serum Tg response to challenge by bovine TSH. Only minute amounts of Tg-related antigens were detected by RIA in the goitrous tissue (HSN, 0.82 mg/g, compared to 70-90 mg/g in normal thyroid tissue), as confirmed by sodium dodecyl sulfate-agarose gel electrophoresis that indicated the virtual absence of Tg. The Tg messenger ribonucleic acids (mRNAs) from controls and HSN thyroid tissue were first reverse transcribed and then divided into several portions from positions 57-8448; the resulting complementary DNAs were, in turn, amplified by reverse polymerase chain reaction. The amplification of nucleotides 5165-6048 from control thyroid tissue Tg mRNA showed a fragment of 884 base pairs (bp). In contrast, the fragment present in the HSN was +/- 750 bp and lacked the normal fragment. The sequencing of the smaller fragment revealed that 138 bp were missing between positions 5590-5727 of the HSN Tg mRNA. This deletion does not affect the reading frame of the resulting mRNA and is potentially fully translatable into a Tg polypeptide chain that is shorter by 46 residues. A cysteine residue is maintained by the junction between the proximal T from leucine 1831 and the distal GT from cysteine 1877. DNA genomic polymerase chain reaction amplification excludes a deletion in the Tg gene and indicates that the deleted 138-nucleotide sequences lie in the same exon. The functional consequences of the deletion are not entirely clear, but it is conceivable that the excision of this segment of the Tg molecule could affect the protein structure, resulting in its premature degradation, very low colloid storage, and diminished thyroid hormone production rate.

A novel mutation of the luteinizing hormone receptor gene causing male gonadotropin-independent precocious puberty.

Familial male-limited precocious puberty (FMPP) is an autosomal dominant gonadotropin-independent disorder. Affected males generally develop signs of precocious puberty in early childhood. They typically show Leydig cell hyperplasia and increased testosterone production typical for their age, whereas circulating LH concentrations remain prepubertal. Several dominant point mutations of the LH receptor gene were identified in pedigrees with familial male-limited precocious puberty and were shown to cosegregate with the disease. Here we report a novel heterozygote point mutation in the LH receptor gene of a Brazilian boy with gonadotropin-independent precocious puberty. This mutation substitutes alanine 568 with valine at the carboxyterminus of the third cytosolic loop of the LH receptor. The unoccupied mutant receptors confer constitutive activation of adenyl cyclase activity when expressed in COS-7 cells, resulting in 4-fold higher cAMP concentrations over baseline compared with cells expressing an equivalent number of wild-type receptors. The affinity of the mutant receptors to 125I-labeled human LH was not altered compared with the wild type. Mutations of the homologue alanine residue in the alpha 1-adrenergic (in vitro), FSH (in vitro), and TSH (naturally occurring) receptors also result in constitutive adenyl cyclase activation, suggesting that this alanine residue is crucial for signal transduction and a potential site for upregulatory/oncogenic mutations in G-protein coupled receptors.

Growth hormone pulsatility in active and cured acromegalic subjects.

GH secretion in normal subjects is periodic, with pulses prevailing during sleep. During the day (basal secretion), GH levels are, in general, undetectable. We studied GH secretion by cluster analysis, collecting samples every 20 min for 24 h in 44 subjects: 11 patients with active acromegaly; 16 "cured" acromegalics, and 17 normal subjects. The purpose of this study was to compare GH secretion between patients with active acromegaly and "cured" patients and between "cured" acromegalic patients and normal controls. The number of pulses detected through the 24-h GH profile was not different between acromegalic patients regardless of disease activity (17.5 +/- 4.4 vs. 15.0 +/- 6.0, respectively), but was different when active acromegalic patients and normal controls were compared (8.1 +/- 1.0; P < 0.05) and when cured acromegalic patients and normal controls were compared (P < 0.05). The GH pulsatile secretion/total GH secretion ratio was higher in normal controls than in acromegalic patients regardless of disease activity. We concluded that 1) the increases in GH pulsatility in active and cured acromegalic patients are similar, but most of the 24-h GH secretion is nonpulsatile; 2) half of the GH secretion in normal subjects occurs during pulses; 3) cured acromegalic patients, even those with normal GH and insulin-like growth factor I levels, do not recover a normal GH secretory pattern.