Number of autoantibodies and HLA genotype, more than high titers of glutamic acid decarboxylase autoantibodies, predict insulin dependence in latent autoimmune diabetes of adults.

OBJECTIVE: In latent autoimmune diabetes of adults (LADA), the progression into insulin-dependent diabetes is usually faster than in type 2 diabetes (T2D) but the factors influencing this progression are not completely known. In this study, we searched for sensitive markers associated with early development of insulin dependence. DESIGN: The screening of 5568 T2D patients for glutamic acid decarboxylase autoantibodies (GAD65Ab) identified 276 LADA patients (M=131; F=145) and in 251 of them, tyrosine phosphatase-2 (IA-2Ab) and thyroperoxidase autoantibodies (TPOAbs), some clinical features and genotype variation of the main type 1 diabetes (T1D) disease susceptibility loci (HLA-DRB1 and HLA-DQB1) were analyzed. RESULTS: Four years after the diagnosis of diabetes, high GAD65Ab titer was not significantly associated with faster progression toward insulin deficiency (P=0.104). Patients with GAD65Ab and TPOAb or IA-2Ab or triple positivity for both islet and TPOAbs (GAD65Ab/IA-2Ab/TPOAb) showed a significantly faster disease progression (P=0.002). Among 104 TPOAb-positive LADA patients, 10 received replacement therapy (l-thyroxine), 43 showed high TSH levels (62.7% developed insulin dependence), and 3 had hyperthyroidism treated with methimazole. Multivariate analysis revealed a significant effect on disease progression only for TPOAb (P=0.022), female gender (P=0.036), low body mass index (BMI; P=0.001), and T1D high/intermediate risk HLA-DRB1/DQB1 genotypes grouped (P=0.020). CONCLUSIONS: High GAD65Ab titers per se are not a major risk factor for disease progression in LADA, while the number of positive autoantibodies and HLA DRB1-DQB1 genotypes at high risk for T1D are significant predictors. Moreover, clinical characteristics such as low BMI and female gender are more likely to identify patients who will require insulin therapy within 4 years of diagnosis.

Physiological and genetic characterization of the Gly40Ser mutation in the glucagon receptor gene in the Sardinian population. The Sardinian Diabetes Genetic Study Group.

A Gly40Ser amino acid substitution in the glucagon receptor gene has been associated with non-insulin-dependent diabetes mellitus (NIDDM), but the questions raised about its physiological implications have not been resolved. The aim of this study was to determine the frequency of the Gly40Ser mutation in different regions of Sardinia and to investigate the physiological implications of the mutation in glucose and insulin homeostasis. We studied a population of 691 subjects selected on the basis of their Sardinian origin. Only heterozygous subjects were found, 21 of 574 (3.6%) in NIDDM patients and 5 of 117 in non-diabetic subjects (4.2%). In northern Sardinia 3.4% of the NIDDM patients were carriers of the Gly40Ser substitution, 1.4% in central Sardinia, while 7.6% carried the substitution in the Southern part. No significant differences were found between hypertensive and normotensive subjects with respect to the presence of Gly40Ser. Ten subjects with Gly40Ser were carefully matched for diabetic state, BMI, age, sex, and geographical origin with 10 patients with Gly40, and a glucagon infusion test was performed using 1, 3, 9 and 27 ng glucagon kg-1.min-1 for 30 min. Blood for determination of glucose, glucagon, and insulin concentrations was drawn at 15-min intervals from the Controlateral arm. Plasma glucagon increased dose-dependently during the infusion with no significant difference between the two groups. Carriers of Gly40Ser had a significantly lower (p < 0.02) increase in plasma glucose concentration in response to glucagon infusion compared to Gly40 homozygous subjects at all times, while the plasma insulin increase was not significantly different at any time. In conclusion, our results indicate that the Gly40Ser variation is not associated with NIDDM in the Sardinian population and that its frequency varies in different parts of Sardinia. Moreover in vivo Gly40Ser plays a physiological role in the glucose homeostasis under glucagon control both in NIDDM and non-diabetic subjects. This latter result suggests that this amino acid substitution in the glucagon receptor may lead to a decreased blood glucose concentration because of the reduced stimulation of liver glucose output via the glucagon receptor.

Long-term treatment of Nelson's syndrome by octreotide: a case report.

Medical management of Nelson's syndrome by drugs such as bromocriptine, sodium and magnesium valproate has provided disappointing or, at least, controversial results. We report here on the results of long-term (2 yr) treatment with the somatostatin analogue octreotide (300 micrograms daily sc) in one patient affected by Nelson's syndrome occurring after bilateral adrenalectomy for Cushing's syndrome. During treatment, skin hyperpigmentation and serum ACTH levels decreased dramatically and a slight (about 10%) reduction in tumor size, as assessed by computerized tomography, was also observed. These results suggest that octreotide may be useful for the medical management of Nelson's syndrome.

Octreotide treatment does not affect the size of most non-functioning pituitary adenomas.

The somatostatin analogue, octreotide (OC) has commonly been used in the management of growth hormone- and thyrotropin-secreting pituitary tumors, and shown to be effective both on hormone production and tumor size. Because OC receptors may be expressed also in some nonfunctioning pituitary adenomas, it has been postulated that OC might play a role in the treatment of these tumors as well. In the present study, the morphological effects of OC administration, as assessed by computer tomography (CT) scan, were evaluated in 8 patients (5 men, 3 women, age range 25-79 yr) affected by non-functioning pituitary tumors. The drug was given sc at the dose of 100 micrograms tid for 3-6 months. No significant change in visual field or tumor size occurred after OC treatment in 7 patients, whereas one showed a significant improvement of visual field associated with a decreased tumoral mass. These data suggest that OC is not an effective drug in the management of nonfunctioning pituitary adenomas.

Absence of serum thyroid hormone autoantibodies in patients chronically treated with amiodarone.

The role of iodine in the pathogenesis of thyroid hormone autoantibodies (THAA) was evaluated in a large series (n = 223) of patients submitted to chronic treatment (3-36 months) with the iodine-rich drug, amiodarone. Positive anti-T3 autoantibody (AbT3) tests were found only in one patient, whereas tests for anti-T4 autoantibody (AbT4) were negative in all cases. Likewise, the incidence of THAA in the control groups of patients with spontaneous thyroid disorders was low. The overall prevalence of THAA in the present series of 803 patients was 1.2% for AbT3 and 0.1% for AbT4. The present data strongly suggest that iodine plays a minor role, if any, in the occurrence of THAA.