Spurious elevation of plasma immunoreactive adrenocorticotropic hormone in cyclic Cushing's syndrome.

We studied a 40-year-old woman with cyclic Cushing's syndrome who demonstrated abnormal high-dose dexamethasone suppression and metyrapone stimulation tests. These results, associated with persistent elevations of plasma adrenocorticotropic hormone (ACTH) levels, suggested ectopic secretion of ACTH. Surprisingly, an adrenal adenoma with atrophy of the contralateral adrenal gland was found at exploratory laparotomy. Subsequent ACTH determinations that extract ACTH from the plasma before assay suggested that the apparent increase in ACTH concentration in our routine assay was due to the presence of an interfering substance(s). We conclude that the diagnosis of Cushing's syndrome continues to depend on a battery of adrenal function tests and radiographic procedures and recommend that measurements of ACTH be performed only after extraction of ACTH from specimens.

Peripheral resistance to thyroid hormone in a family: heterogeneity of clinical presentation.

We describe a family with thyroid hormone resistance. Juvenile Graves disease was diagnosed in the propositus, an 8-month-old boy. He was initially given propylthiouracil, and at 22 months of age underwent subtotal thyroidectomy. A diagnosis of hyperthyroidism was made in a younger sister at 3 months of age. Because of the unusual occurrence of juvenile Graves disease in two siblings, we evaluated the parents. The mother was euthyroid on physical examination and by thyroid hormone measurements. The father, although clinically euthyroid, had markedly elevated thyroid hormone values. In the three affected members, serum thyrotropin concentrations and results of thyrotropin-releasing hormone infusion tests were inappropriate for the elevated serum thyroid hormone levels. The father was given increasing doses of triiodothyronine. Complete suppression of TRH-induced TSH release did not occur until a daily dose of 300 micrograms triiodothyronine was administered. Furthermore, this large dose of T3 did not produce clinical evidence of hyperthyroidism or result in changes in his systolic ejection time intervals. This family therefore had the unusual feature of clinical heterogeneity. The two children had mainly pituitary resistance to thyroid hormone and were hyperthyroid; the euthyroid father, on the other hand, had generalized tissue resistance to thyroid hormone.

Ketotic hypoglycaemia.

Ketotic hypoglycaemia is the most common form of childhood hypoglycaemia. This disorder classically manifests itself between the ages of 18 months and 5 years, and generally remits spontaneously before 8 or 9 years of age. A presumptive diagnosis is made by documenting a low blood sugar in association with ketonuria, ketonaemia and typical symptoms of hypoglycaemia. The definitive diagnosis is established by demonstrating an inability to tolerate a provocative ketogenic diet, or a fast. Susceptible or affected children develop severe hypoglycaemia and ketosis on this diet within 24 hours. Plasma alanine concentrations on either a normal or ketogenic diet were significantly lower in ketotic hypoglycaemic children compared with normal children. In contrast to adults, even normal children develop hypoglycaemia and ketonaemia when calorically deprived for relatively short periods of time (32 to 36 hrs).

Constant intravenous insulin infusion during labor and delivery in diabetes mellitus.

We treated 30 diabetic women (31 pregnancies) during the peripartum period with a continuous insulin infusion. A mean infusion rate of 1.0 micron/h maintained the mean plasma glucose concentration below 100 mg/dl in 84% of the patients; the plasma glucose concentration was below 100 mg/dl within an hour of delivery in 71% of the women. Mild hypoglycemia developed during the infusion in three women and after delivery in another patient. Only two infants of the diabetic mothers developed transient and asymptomatic hypoglycemia. We conclude that continuous insulin infusion is a practical, safe, and effective method for treating diabetic mothers during the peripartum period and suggest that this technique may decrease the frequency and severity of neonatal hypoglycemia.

Differences in circulating gluconeogenic substrates during short-term fasting in men, women, and children.

To determine whether the differences in fasting glucose responses in men, women and children could be related to differences in glucoregulatory hormone secretion or availability of circulating gluconeogenic substrates, 20 adults (10 men and 10 women) were fasted for 86 hr and 15 children (6.1 +/- 0.8 yr, mean +/- SE) were fasted for 30 hr. Circulating concentrations of glucose, ketone bodies, potential gluconeogenic substrates and glucoregulatory hormones were determined at frequent intervals. In the postprandial state (1-14 hr fasting), substrate and hormone concentrations were similar in all groups with the exception of plasma glutamine concentrations which were higher in men (640 +/- 20 microM) than in women of children (490 +/- 20 microM and 480 +/- 50 microM, respectively, p less than 0.01 for both). Following 30 hr fasting children had the lowest glucose (53 +/- 3 mg/dl) and alanine (167 +/- 17 microM) concentrations and men had the highest (72 +/- 3 mg/dl and 279 +/- 16 microM, respectively) whereas those of women were intermediate (64 +/- 3 mg/dl and 226 +/- 19 microM. respectively). Following 30 hr of fasting betahydroxybutyrate concentrations were highest in children and lowest in men (the children, 3.7 +/- 0.4 mM; women, 1.7 +/- 0.2 mM and men 0.9 +/- 0.2 mM, p less than 0.02 between all groups). An inverse relationship (p less than 0.001 was observed between beta-hydroxybutyrate and glucose concentrations throughout the fast for each group (r greater than 0.92). Although plasma cortisol concentrations were higher in women and children when compared to those of the men, no differences in growth hormone, glucagon, or insulin concentrations were observed among the three groups studied. Differences in plasma substrate responses to fasting among the groups studied may reflect differences in glucose requirements among men, women and children, as well as the relative availability of both gluconeogenic substrate and ketone bodies.

Elevation of the free thyroxine index in psychiatric patients.

We calculated a free triiodothyronine (FT3) index on 124 patients who exhibited symptoms and signs of hyperthyroidism and elevations of the free thyroxine (FT4) index on initial screening. A thyrotropin-releasing hormone (TRH) test served as the final arbiter of thyroid function if the clinical presentation was not characteristic of hyperthyroidism or if the FT3 index was not elevated. Forty-one of the 124 patients had normal TRH tests and were thus classified as euthyroid. Of these patients with the so-called euthyroid sick syndrome, 23 had psychiatric disorders. In a separate study, we measured a FT4 index on 100 unselected admissions to the psychiatric ward. Of six patients with elevated FT4 values, only one had hyperthyroidism. We conclude that false positive FT4 index elevations occur commonly in psychiatric patients. The mechanism(s) for the FT4 index elevations remain obscure. Despite some limitations, the TRH test is a valuable diagnostic adjunct for diagnosing hyperthyroidism in the mentally ill patient when other tests and serial observations are inconclusive.

Thyroxine toxicosis. A common variant of hyperthyroidism.

To determine the frequency of thyroxine (T4) toxicosis, we calculated a free triiodothyronine index (FT3I) on 124 patients who displayed elevations of the free T4 index (FT4I) on initial screening. If the clinical presentation was not characteristic of hyperthyroidism or if the FT3I was not elevated, a thyrotropin-releasing hormone (TRH) test was performed. Of 83 hyperthryoid patients, 70 displayed elevations of both the FT4 and FT3 indices. Thirteen patients, however, had elevations of the FT4I alone. This frequency of T4 toxicosis is higher than generally appreciated. Forty-one patients, most of whom were ill with nonthyroidal diseases, had normal TRH test results and were classified euthyroid. We conclude that FT4I elevations owing to T4 toxicosis and nonthyroidal illnesses are common and that the laboratory differentiation between the syndromes may be difficult.

Defective activation of the pyruvate dehydrogenase complex in subacute necrotizing encephalomyelopathy (Leigh disease).

Autopsy examination confirmed the diagnosis of subacute necrotizing encephalomyelopathy (SNE) in a 7-month-old male infant who underwent several metabolic studies before death. Intermittent lactic acidemia and fumaric aciduria, an extreme hyperglycemic response to an intravenous bolus of alanine, and an elevated total body flux rate of glucose (58.4 mumoles . kg-1 . min-1) suggested a disturbance in the oxidative decarboxylation of pyruvate. Enzymological studies of postmortem samples revealed low nonactivated pyruvate dehydrogenase activity in liver (19.4%) and brain (53.8%). The lowest brain pyruvate dehydrogenase activities were noted in the midbrain and pontine regions. Supramaximal activation of the hepatic pyruvate dehydrogenase complex (135% of control values) occurred in vitro. Spontaneous reactivation following in vitro inactivation of the complex with adenosine triphosphate was significantly less (p less than 0.02) in the patient's samples compared to controls. The biochemical defect was not apparent in fibroblasts. These enzymological observations point to an in vivo defect in the activation mechanism of the pyruvate dehydrogenase complex as the biochemical disturbance in SNE. The findings suggest that dichloroacetate may be beneficial in treating SNE.

Starvation diabetes in the rat: onset, recovery, and specificity of reduced responsiveness of pancreatic beta-cells.

A 24-h starvation markedly diminished the stimulant action of 8 mM glucose on insulin secretion from isolated perifused rat islets of Langerhans. The response to a supramaximal glucose stimulus (27.5 mM) remained normal, but prolonged fasting (48 or more) also reduced its efficacy. Refeeding of 24-h fasted animals resulted in complete restoration of glucose sensitivity within 24 h. The responses to glyceraldehyde (2 mM) and alpha-ketoisocaproate (8 mM) at concentrations which elicit approximately half-maximal stimulation were unaltered by a 24-h fast, while that to a half-maximally effective dose of mannose (15 mM) was decreased. Theophylline (5 mM) could not normalize the reduced secretory response to glucose seen in this state. The islets' ability to metabolize glucose, using various in vitro pretreatment protocols and different incubation times, was not affected by a 24-h fast. Mannose and glyceraldehyde metabolism were also unaltered. Prolonged fasting (48 h) reduced glucose metabolism by 25% at both 8 and 27.5 mM. The acute adaptive changes in islet sensitivity to moderate glucose and mannose concentrations during short term fasting (24 h) cannot be explained by an altered usage of the added hexoses.

Cure of acromegaly by operative removal of an islet cell tumor of the pancreas.

We studied a 30 year old woman in whom acromegaly was cured by operative removal of a large cystic beta cell adenoma of the pancreas. We detected substantial amounts of immunoreactive human growth hormone (hGH)-like activity in a tumor tissue extract. Extracts of the tumor and a normal human pituitary gland eluted from a Sephadex G-75 column in two identical peaks. Serial dilutions of the tumor extract displaced radioactive 125I hGH parallel to a standard curve. Surprisingly, an extract of a normal human pancreas contained large amounts of hGH-like activity and gave results similar to those of the tumor extract on gel chromatography and on serial dilution displacement in the growth hormone immunoassay. Paper electrophoretic studies of 125I hGH after incubation with normal pancreatic and tumor extracts with and without enzyme inhibitors suggested that pancreatic proteolytic enzymes damaged the 125I hGH used in growth hormone radioimmunoassay and produced a false detection of hGH.

The clinical and biochemical implications of pyruvate carboxylase deficiency.

A 10 month old female infant was evaluated for severe lactic acidosis. Clinically she was well nourished and had a substantial amount of adipose tissue despite recurrent episodes of acidosis. Her psychomotor development was retarded, her movements were dystonic and generalized seizures punctuated her course. Metabolic abnormalities included elevated blood concentrations of lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, alanine, proline and glycine, decreased blood concentrations of glutamine, aspartate, valine and citrate, and intermittent elevations of serum cholesterol. A trial on a high-fat diet worsened the clinical condition and intensified the ketoacidosis and hyperalaninemia. Analysis of hepatic tissue obtained by open biopsy revealed increased concentrations of lactate, alanine, acetyl-CoA and other short-chain acyl-CoA esters, and decreased concentrations of oxaloacetate, citrate, alpha-ketoglutarate, malate and aspartate. The blood and tissue metabolic perturbations reflected a deficiency of hepatic pyruvate carboxylase. The apparent Km of hepatic citrate synthase for oxaloacetate was 4.6 micrometer. Calculated tissue oxaloacetate concentrations were 0.50--0.84 micrometer suggesting that tricarboxylic acid cycle activity was severely limited by the decreased availability of this substrate. An iv glucose tolerance test resulted in the paradoxical synthesis of ketone bodies. This observation, coupled with the intermittent hypercholesterolemia and the increased tissue acetyl-CoA concentrations, suggests that pyruvate carboxylase is important in modulating the fractional distribution of intracellular acetyl-CoA between the tricarboxylic acid cycle, the beta-hydroxy-beta-methyl-glutaryl-CoA cycle (and the synthesis of cholesterol and ketone bodies), and fatty acid synthesis. Treatment in future cases might be directed toward increasing tissue concentrations of oxaloacetate.

Glucagon, insulin and glucose response to physiologic testing in normal and massively obese adults.

Ten normal adults and ten nondiabetic massively obese subjects were studied following 4--7 days on identical diets. Intravenous arginine challenge resulted in similar glucose and glucagon responses and threefold greater integrated insulin responses in the obese when compared to the normal subjects. Following oral glucose, glucagon responses were similar, whereas both basal and integrated insulin values were higher in the obese subjects. Basal and integrated insulin concentrations were greater during intravenous glucose testing in the obese subjects, whereas similar glucagon suppression was observed in both groups. Hourly blood samples obtained during a 24-hr period revealed that the obese glucose profile differed significantly from the normals. Insulin values were two- to four-fold higher in the obese subjects, whereas no significant difference was observed in the glucagon concentrations. The nadir and peak glucagon concentrations for both groups occurred at 8:00 a.m. and 8:00 p.m., respectively, and were positively correlated with plasma amino acid values, and were similar in both groups.

Glucose and 3-O-methylglucose protection against alloxan poisoning of pancreatic alpha and beta cells.

Alloxan infused into the isolated perfused rat pancreas caused transient insulin secretion release. Alloxan poisoning also prevented subsequent induction of glucose-mediated unsulin release and also prevented the inhibition of glucagon release by glucose. Glucose or 3-O-methylglucose infused simultaneously with alloxan protected the alpha- and beta-cell, allowing subsequent glucose inhibition of glucagon secretion and stimulation of insulin release. The above alloxan effects were dose-related, the alpha-cell being one fourth as sensitive to alloxan as the beta-cell. The data indicate that (1) alloxan and glucose suppression of amino-acid-stimulated glucagon secretion is independent of concomitant insulin secretion; (2) alloxan, like glucose, affects alpha-and beta-cells directly, stimulating the beta-cell and inhibiting the alpha-cell; and (3) alloxan acts on a glucoreceptor system with comparable physicochemical characteristics common to both cell types.

Effects of iodoacetate, mannoheptulose and 3-O-methyl glucose on the secretory function and metabolism of isolated pancreatic islets.

The ability of iodoacetate, mannoheptulose, and 3-O-methyl glucose to alter islet cell metabolism and glucose-stimulated insulin secretion was examined. A method for the sequential analysis of the releasing and fuel function of glucose in isolated islets was applied. Insulin release was measured by radioimmunoassay and the metabolism of glucose by determining the rate of tritiated water production from [5-3H]glucose and lactate accumulation. It was found that iodoacetate, in the range of 0.2-1.0 mM, inhibited the metabolism of glucose linearly while release was not blocked until metabolism was reduced by 30-40%. The KI for both processes, release and metabolism, was the same. Pyruvate did not protect against or reverse the effects of iodoacetate. Mannoheptulose inhibited both release and metabolism half-maximally at about 5 mM when 27.5 mM glucose was used as the stimulatory agent. A mannoheptulose-resistant component of glucose metabolism, amounting to 30% of the maximal rate was observed. 3-O-Methyl glucose had no effect on insulin release but reduced glucose utilization and lactate production from low glucose. The results are discussed in light of the two prevailing hypotheses explaining glucose induced insulin release, i.e., the receptor and the metabolism hypotheses.