PubMed Health⌕ Search

Biomedical subjects

N S Levitt

Publications and source records attributed to N S Levitt.

At least 55 records · Page 3Linked to original sources
PubMed1995

Pituitary function after selective adenomectomy for Cushing's disease.

This retrospective analysis was undertaken to determine whether selective adenomectomy for Cushing's disease can achieve acceptable cure rates while causing minimal pituitary dysfunction. Tumour size, histology and pituitary function were evaluated in 34 consecutive patients (26 F: 8 M, mean age 33.6 years) undergoing transphenoidal adenomectomy for Cushing's disease from 1975 to 1992. Follow-up averaged 5.8 years. Cure was defined as resolution of symptoms and signs and normalization of urinary cortisol excretion. Sixty-three per cent of patients achieved cure after selective adenomectomy, repeat adenomectomy cured an additional four patients. Twenty-eight per cent required bilateral adrenalectomy and/or pituitary irradiation. Postoperative pituitary function remained completely intact in 81%. Secondary hypogonadism occurred in 8%, hypothyroidism in 155 and permanent diabetes insipidus in 4%. There was recurrence in 26% after a mean of 4.6 years (range 1-7). It is concluded that selective adenomectomy can achieve acceptable cure rates with a low prevalence of postoperative hypopituitarism, although an increase of recurrence may be the result of conservative surgery.

Adenoma↗
PubMed1994

The spectrum of endocrine dysfunction in active pulmonary tuberculosis.

OBJECTIVE: Substantial variation in the prevalence (0-55%) of hypoadrenalism in tuberculosis (TB) has been reported. The aim of this study was to prospectively evaluate adrenal, thyroid and gonadal function in patients presenting with active pulmonary TB. DESIGN: A prospective study of 50 patients admitted to a single hospital. PATIENTS: Fifty hospitalized adults with newly diagnosed sputum positive pulmonary TB (mean age 38 years, mean body mass index 18 kg/m2, mean albumin 28 g/l) were studied. MEASUREMENTS: Adrenal reserve was assessed by intravenous tetracosactrin administration with measurement of basal and stimulated cortisol concentrations. Basal ACTH, thyroid and gonadal hormones were also measured. RESULTS: The mean basal serum cortisol was 625 nmol/l (range 394-1185). Basal plasma ACTH was undetectable (< 4.4 pmol/l) in 32, normal in 17 (mean 11.45, range 4.4-24.9 pmol/l) and elevated in one (54.2 pmol/l) subjects and did not correlate with cortisol. The mean increment in cortisol following tetracosactrin was 256 nmol/l (range 0-650) and was unrelated to basal cortisol or ACTH. All 50 patients had a stimulated plasma cortisol exceeding 550 nmol/l, indicating intact adrenal reserve. Ninety-two per cent of patients had the sick euthyroid syndrome, 72% of males had hypogonadotrophic hypogonadism and 4% of patients tested positive for the human immunodeficiency virus. CONCLUSIONS: Hypoadrenalism is uncommon in active pulmonary TB despite frequent dysfunction of the thyroid and gonadal axes.

Adolescent↗
PubMed1993

Quantitative evaluation of the effect of low-intensity exercise on insulin secretion in man.

We studied insulin secretion rates (ISR) during low-intensity exercise (40% peak aerobic capacity [VO2]) in 12 normal subjects to assess the contribution of altered insulin secretion to the reduction in peripheral insulin concentrations associated with exercise. ISR were calculated by a previously validated method of two-compartment analysis of peripheral C-peptide concentrations using individual parameters derived following a bolus injection of biosynthetic human C-peptide. In addition, the effect of low-intensity exercise on kinetic parameters of C-peptide was evaluated. The results showed that low-intensity exercise did not significantly affect C-peptide kinetics. Peripheral insulin concentrations and ISR decreased to a similar degree throughout exercise. There was a mean maximum decrease in serum insulin concentrations from 42 +/- 5.4 pmol/L basally to 24 +/- 2.6 pmol/L, constituting a 51% +/- 5.9% decrease (P < .001), and ISR decreased from 85.7 +/- 11.9 pmol/min to a nadir of 45.6 +/- 10.6 pmol/min (P < .001), a 48% +/- 8.4% decline. Plasma glucose and glucagon concentrations did not change significantly either during or after exercise, although there was a matched twofold increase in glucose utilization and disposal rates. We suggest that the reduction in peripheral insulin concentrations during exercise is due to reduced insulin secretion.

Adult↗
PubMed1993

The prevalence and identification of risk factors for NIDDM in urban Africans in Cape Town, South Africa.

OBJECTIVE: To determine the prevalence of NIDDM and associated risk factors in urban Africans in Cape Town, South Africa. RESEARCH DESIGN AND METHODS: With a three-stage, proportional, stratified, random cluster method, we sampled 1000 Africans, > 30 yr of age, living in African residential areas in Cape Town. We assessed glucose tolerance with a 75-g oral glucose tolerance test, according to World Health Organization criteria, and obtained anthropometric and demographic data. RESULTS: The response rate was 79%. The prevalence of NIDDM was 8.0% (confidence interval 5.8-10.3%), age-adjusted to world population figures and that of impaired glucose tolerance, 7.0% (confidence interval 4.9-9.1%). Multivariate analysis indicated that increased age (odds ratio 4.18), upper-segment fat distribution (odds ratio 2.94), proportion of life spent in an urban area (odds ratio 2.32), and obesity (odds ratio 2.31) were significant independent risk factors for NIDDM. In contrast, sex, family history, alcohol intake, and physical activity were not independent risk factors. Only increased age (odds ratio 4.06) was a significant risk factor for impaired glucose tolerance. CONCLUSIONS: The prevalence of NIDDM in urban Africans in Cape Town, South Africa, is moderately high, and considerably higher than previous reports from Africa. The association of NIDDM with urbanization has important implications in view of the large-scale urbanization occurring in southern Africa.

Adult↗
PubMed1990

Pentavalent technetium-99m (V)-DMSA uptake in a pheochromocytoma in a patient with Sipple's syndrome.

This case report describes 99mTc(V)-dimercaptosuccinic acid (DMSA) accumulation in a pheochromocytoma in a patient with Sipple's syndrome. Scintigraphy with 99mTc(V)-DMSA demonstrated uptake in medullary carcinoma of the thyroid gland (MCT). Iodine-131 metaiodobenzylguanidine (MIBG) scintigraphy showed the bilateral pheochromocytomas but did not demonstrate uptake in the MCT.

3-Iodobenzylguanidine↗
PubMed1988

Oxygen uptake kinetics during exercise in diabetic neuropathy.

To assess the effect of autonomic and sensorineural dysfunction on O2 uptake kinetics, we studied the exercise response of seven diabetic humans having peripheral sensory and cardiac autonomic neuropathy, eight diabetics without neuropathy, and eight normal subjects. Maximal O2 uptake (VO2max), ventilatory anaerobic threshold, and O2 uptake kinetics were assessed. Metabolic control was optimized 12 h prior to and during testing by intravenous insulin infusion. Patients with diabetic neuropathy had a reduced VO2max [83 +/- 6% predicted vs. 104 +/- 6% (nonneuropathic diabetics) and 107 +/- 5% (normals); P less than 0.05]. However, there was no difference in ventilatory anaerobic threshold [14.8 +/- 0.9 (neuropathic diabetics) vs. 18.0 +/- 1.0 (nonneuropathic diabetics) and 16.7 +/- 1.5 ml O2.kg-1.min-1 (normals); P greater than 0.25]. The phase I increment in O2 uptake (VO2) and estimated cardiac output and the time constant of VO2 during constant-load exercise at 40% VO2max also were similar in all groups. We propose that the instantaneous increase in VO2 and cardiac output at exercise onset in diabetes with impaired neurogenic reflexes is caused primarily by mechanical and metabolic events in exercising muscle that cause venous compression and vasodilation.

Adult↗
PubMed1984

Arginine hydrochloride stimulation of serum potassium and aldosterone is enhanced by somatostatin-28.

Potassium, aldosterone and insulin responses to arginine infusion were compared in 5 normal men during infusions of somatostatin-14 (SS-14), somatostatin-28 (SS-28) and a control infusion. SS-14 and SS-28 were infused continuously at a rate of 8.6 pmol/min/kg and arginine (0.5 g/kg) was infused from 30-60 min. Following the control infusion with arginine hydrochloride, serum aldosterone and potassium levels increased slightly. The rise in potassium appears to be due to an exchange of cellular potassium for the proton from the arginine hydrochloride. SS-14 had no significant effect on serum potassium or aldosterone but an equimolar dose of SS-28 significantly enhanced the rise in potassium and aldosterone. SS-28 completely inhibited the arginine-stimulated insulin increase while SS-14 only partially inhibited the insulin increase. Since insulin opposes the increase in serum potassium by stimulating cellular uptake of this cation, the enhanced rise in serum potassium in response to arginine hydrochloride during the SS-28 infusion is likely due to the potent insulin suppressing effect of SS-28. The rise in serum aldosterone is directly related to the degree of elevation of serum potassium. These findings caution against the infusion of SS-28 during an arginine stimulation test.

Acid-Base Equilibrium↗
PubMed1983

Somatostatin-28 and somatostatin-14 suppression of arginine-, insulin-, and TRH-stimulated GH and PRL secretion in man.

GH and PRL responses to arginine infusion and to the combined pituitary stimulation test (0.1 u/kg of insulin, 200 micrograms of TRH, 100 micrograms of LHRH) were compared in five normal men during infusions of somatostatin-14 (SS-14) and somatostatin-28 (SS-28), and during control infusions of vehicle alone. SS-14 and SS-28 were infused at a rate of 1.8 nmol/kg over 210 min. Arginine (0.5 g/kg) was infused from 30 to 60 min and the combined pituitary stimulation test commenced at 120 min. Arginine (0.5 g/kg) infused from 30 to 60 min induced an increase in GH secretion in all subjects and this increase was completely abolished in these same subjects when infused with SS-14 and SS-28. Arginine-induced hyperglycaemia was significantly greater during infusion of SS-14 and further enhanced by infusion of SS-28. A small increase in PRL secretion occurred after arginine infusion and this was not inhibited by SS-14 or SS-28. Insulin and TRH administration induced marked increases in both GH and PRL secretion. The mean GH increase was significantly inhibited by SS-14 and SS-28 up to 165 min but not thereafter. The PRL increase was significantly inhibited by SS-28 but not by SS-14 and this greater efficacy was also indicated by administering different doses of SS-28 to one subject. Taken together with the demonstration that SS-28 is released from the median eminence, these findings indicate that SS-28 has a hormonal role in the regulation of GH and PRL secretion.

Adult↗
PubMed1983

Inhibition of pancreatic hormone secretion by somatostatin-28 and somatostatin-14 in man.

The effects of a 210 min infusion of 1.8 nmol/kg somatostatin-14 (SS-14), somatostatin-28 (SS-28), and vehicle (Haemaccel) alone, on arginine- and insulin-stimulated release of pancreatic hormones were tested in 5 normal male subjects. Arginine administered at 30-60 min induced an increase in plasma glucose concentrations which was enhanced by SS-14 and further increased by SS-28. SS-28 was more effective than SS-14 in suppressing the arginine-induced secretion of insulin. Arginine-stimulated and insulin-stimulated (at 120 min) glucagon release was equally suppressed by SS-14 and SS-28, as was insulin-stimulated pancreatic polypeptide secretion. At the end of the SS-14 infusion the mean plasma somatostatin level was approximately 28% of that which occurred during the SS-28 infusion. The results are discussed in relation to similar studies in vitro and in vivo in laboratory animals and to a possible role of the two forms of SS in carbohydrate homeostasis.

Adult↗
PubMed1982

Somatostatin-28 inhibits thyroid-stimulating hormone release in man.

The effects of an equimolar (1,8 nmol/kg body weight) infusion of somatostatin-28 (SS-28) and somatostatin-14 (SS-14) on the thyroid-stimulating hormone (TSH) response to a combined pituitary function test consisting of 200 micrograms thyrotrophin-releasing hormone (TRH) as well as 100 micrograms luteinizing hormone-releasing hormone (LH-RH) and insulin 0.1 U/kg were compared in 5 normal men. SS-28 significantly inhibited the TSH response to TRH compared with the control infusion. SS-14 was ineffective in 1 subject but overall did not differ significantly from SS-28. In 1 of the subjects the inhibitory effects of SS-28 on the TSH response was determined at three different doses of SS-28. In this subject SS-28 was found to be approximately 16 times more potent than SS-14 in the inhibition of TSH release. Suppression of TSH by SS-28 adds further support for a hormonal role for the peptide.

Adult↗
PubMed1982

Guar biscuits in the diabetic diet.

A new type of guar-containing biscuit has been developed and incorporated into the diabetic diet in both short- and medium-term studies. It has been found to be effective in reducing the postprandial rise in the blood glucose level and in improving glycaemic control, as shown by reduced fasting blood glucose values and decreased 24-hour urinary glucose excretion. This form of guar has proved to be palatable and acceptable to patients. It was effective in smaller quantities than have previously been tested and may prove a valuable adjunct in the treatment of diabetes.

Blood Glucose↗
PubMed1982

Somatostatin-28 inhibits LHRH-stimulated gonadotrophin secretion in man.

The LH and FSH responses to 100 micrograms LHRH in a combined pituitary stimulation test were compared to five normal men during infusions of somatostatin-28 (SS-28) and somatostatin (SS-14) and during control infusions of haemacel. SS-28 and SS-14 were administered in equimolar concentrations of 1.8 nmol/kg body weight over 210 min and LHRH was injected as a bolus at 120 min after commencement of the infusion. SS-28 significantly reduced both LH and FSH responses to LHRH compared with control infusions. SS-14 did not significantly alter the FSH response but caused a significant reduction in the LH concentration 75 and 90 min after LHRH injection. These findings demonstrate that SS-28 has distinct biological activity in addition to its role as a putative precursor of SS-14. Inhibition of gonadotropin hormone secretion by SS-14 and SS-28 suggest that these hypothalamic peptides may play a part in the regulation of LH and FSH secretion.

Adult↗
PubMed1981

Peripheral plasma somatostatin-like immunoreactive responses to insulin hypoglycemia and a mixed meal in healthy subjects and in noninsulin-dependent maturity-onset diabetics.

We have measured peripheral plasma immunoreactive somatostatin (SRIF-LI) in 10 healthy subjects and 10 noninsulin-dependent maturity-onset diabetics (NIDDM). The mean (+/-SE) basal level of SRIF-LI in NIDDMs of 185 +/- 27 was similar to that of 174 +/- 23.5 pg/ml in age-, weight-, and sex-matched healthy subjects. Insulin hypoglycemia of equivalent magnitude induced a 113 +/- 15.8 pg/ml increase in SRIF-LI 40 min after injection in healthy subjects and no significant change in the NIDDMs. Ingestion of a mixed meal induced a biphasic rise with a mean peak of 75 +/- 30 pg/ml above basal at 15 min and a later peak of 130 +/- 35 pg/ml above basal at 120 min in healthy subjects. In NIDDM, there was no significant rise above basal, and the differences were significant at 15 and 120 min. Our findings are compatible with deficient SRIF release in these NIDDM in whom the deficient SRIF secretion may contribute to the hyperglycemia.

Adult↗
PubMed1980

Synthetic luteinizing hormone-releasing hormone in impotent male diabetics.

We compared the effect of luteinizing hormone-releasing hormone (LH-RH) 500 micrograms 8-hourly and placebo on sexual function in impotent diabetic males. These patients had no obvious vascular or neurological disease and no major psychological disorders to account for their impotence. Basal serum testosterone concentrations were normal in all. Five patients had elevated basal gonadotropin concentrations and/or exaggerated gonadotropin responses to LH-RH. During the first week of the LH-RH treatment there was a significant rise in LH and follicle-stimulating hormone (FSH) concentrations. The LH levels remained elevated throughout the second week of treatment, whereas the FSH returned to pretreatment values. There was no change in hormone concentration during placebo therapy. Clinical responses to treatment were assessed by a self-evaluating questionnaire relating to (i) sexual function and libido; (ii) erectile potency; and (iii) general well-being. There was no significant change within each category, but taken together a significant improvement was found with both LH-RH and placebo treatment. There was no difference between the two forms of treatment.

Adult↗