On the role of dopamine receptors in the naloxone-induced hormonal changes in man

To assess the role of dopamine receptors in naloxone-induced hormonal changes, the effects of dopamine and metoclopramide on anterior pituitary hormone secretion were studied during the infusion of the opiate blocker in normal men. Naloxone stimulated LH and cortisol secretion in all subjects, whereas FSH, TSH, PRL, and GH did not change. The infusion of dopamine completely suppressed the naloxone-induced LH rise; on the contrary, metoclopramide failed to alter the magnitude of the increments in LH observed during the infusion of the opiate blocker. The cortisol response to naloxone remained unchanged during dopamine and metoclopramide infusion. Metoclopramide stimulated PRL and TSH release during naloxone treatment, whereas dopamine suppressed PRL and TSH secretion. The data do not suggest a participation of dopamine receptors in the naloxone-induced hormonal changes in man and confirm a suppressive effect of dopamine infusion on LH release in humans.     

Incidental Papillary Thyroid Carcinoma: Diagnostic Findings in a Series of 287 Carcinomas

The recent increase in the detection of papillary thyroid carcinoma (PTC) has been influenced by the finding of incidental tumours. To this group, carcinomas measuring less than 1 cm (the so-called microcarcinomas) as well as those above 1 cm belong. Analyzing a case series from our own experience, this paper focuses on the current pre-operative diagnostic challenges that can lead to PTC incidental discovery. For this retrospective study, 287 patients with a PTC diagnosis were selected. For each, the following variables were analysed: sex, age, ultrasound (US) appearance, number of thyroid nodules, PTC size, PTC variants and presence of other associated pathology. Pre-operative fine needle aspiration (FNA) results were classified according to the five-tiered SIAPEC system. For 281 patients, the US-guided FNA results were available. Cytohistological correlation was evaluated in terms of FNA sensitivity and false negative rate. An incidental PTC was found in 45.2 % of patients. The majority of these were due to unsuccessful US detection of malignant nodules (103 cases); incorrect cytological diagnosis was responsible for the other 24 cases. The most powerful clinical confounding factors were: multinodular background versus single nodule presentations (p?p?2 cm) due to tumour heterogeneity. Although with limitations related to the tumour’s intrinsic features and the thyroid background, US-guided FNA, especially if performed by a dedicated multidisciplinary team, is a powerful diagnostic tool for detecting malignant thyroid nodules. To the state of the art, we propose a practical clinical-pathological cut-off for this procedure, setting it at 5 mm.     

Metergoline and cyproheptadine suppress prolactin release by a non-5-hydroxytryptaminergic, non-dopaminergic mechanism.

Isolated atria of guinea-pigs were treated with veratrine until the initial signs of toxicity were seen. Ouabain was then added cumulatively, starting with a threshold inotropic concentration, 50 nM, until the tissue became dysrhythmic. It was found that a concentration of ouabain which by itself gave a positive inotropic effect of only 3%, significantly enhanced the toxicity of veratrine. Veratrine had no effect on the (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase) enzyme isolated from guinea-pig ventricle. The conclusion drawn is that at threshold inotropic concentrations of ouabain it is likely that the (Na+ + K+)-ATPase is inhibited rather than stimulated.     

Effect of synthetic LH-RH and hCG administration on plasma testosterone, androstenedione, and estradiol 17beta levels in normal men and in patients with idiopathic oligospermia.

Plasma testosterone, androstenedione, and estradiol 17beta levels were measured in 20 normal men and in 20 patients with idiopathic oligospermia before and after iv hCG (5,000 IU) and synthetic LH-RH (50 microgram) administration. No statistically significant differences in the concentrations of the steroids examined were detected between patients and controls either under control conditions or under exogenous and endogenous gonadotropin stimulation.     

An inhibition of the hypothalamic somatostatinergic tone is not the cause of the enhanced growth hormone response to growth hormone-releasing hormone in patients with liver cirrhosis.

Animal models of liver cirrhosis (LC) display a reduced hypothalamic somatostatinergic tone. To test whether a similar mechanism could explain the enhanced Growth Hormone (GH) secretory response to GH-Releasing Hormone (GHRH), which is seen in human LC, we studied the effect of the cholinesterase inhibitor pyridostigmine (PD), which is able to reduce the release of hypothalamic somatostatin (SS), on the GHRH-stimulated GH secretion. We considered that if PD were unable to increase GH secretion, this would constitute evidence of an already inhibited endogenous somatostatinergic tone. If proved, this in turn could explain the enhanced GH response to GHRH seen in LC. Ten LC patients and nine controls were given GHRH (100 microg, intravenously), or PD (120 mg, orally) plus GHRH. After GHRH alone, the GH peak was four times higher in LC than in controls (40.85+/-15.7 ng/ml in LC and 9.35+/-2.5 ng/ml in controls). In LC, PD administration markedly increased the GH response to GHRH (GH peak: 98.0+/-19.7 ng/ml; +240% vs. GHRH alone). The ability of PD to increase the GH response in patients with LC suggests that in this condition the enhanced GH response to GHRH is not due to a completely inhibited endogenous somatostatinergic tone. SS appears instead to maintain its modulator role on GH secretion in human LC, in contrast with what observed in animal models.     

Is There Anything to the Reported Association Between <Emphasis Type="Italic">Helicobacter pylori</Emphasis> Infection and Autoimmune Thyroiditis?

Higher serological prevalence rates of Helicobacter pylori (Hp) infection have been reported in patients with autoimmune thyroiditis (AT), and it has been suggested that monoclonal antibodies against Cag-A positive Hp strains can cross-react with follicular cells of the thyroid gland. We studied the prevalence of AT and thyroid functional status in patients who underwent gastroscopy for dyspeptic symptoms. Patients were tested for TSH, free thyroid hormones, and antithyroglobulin and antithyroperoxidase antibodies (ATPO). Hp positivity was determined using urea breath test (UBT). Serum samples from 302 patients (59.9% women) were evaluated. One hundred ninety-one subjects (63.2%) were Hp-negative, and 111 of 302 (36.8%) were Hp-positive. Forty-three of 191 Hp-negative patients (22.5%; 95% CI, 17.1–29.0%) had an increase of either antibody, compared to 30 of 111 (27.0%; 95% CI, 19.6–36.0%) Hp-positive patients (P = 0.40). Similar results were obtained using positivity for both antibodies (7.3 vs. 7.2%; P = 1) or for ATPO (18.8 vs. 21.6%; P = 0.54). The prevalences of hypothyroidism (4.7 vs. 5.5%) or hyperthyroidism (5.8 vs. 5.5%) were also similar (P = 0.95). Hormonal levels were not different in the two groups (P > 0.22 in all cases). The previously reported association between AT and Hp infection was not observed in our study. Infection by Hp does not appear to increase the risk of AT in individuals with dyspeptic symptoms, and screening for this condition in patients with a positive UBT is not indicated.     

Effect of LRH on gonadotropin secretion in newborn male infants.

The concentrations of LH and FSH were measured in eight male newborn babies, aged 4-6 h, before and after the administration of 25 micrograms synthetic LHR. A comparison was performed with six control newborns receiving normal saline. Both LH and FSH rose significantly in all subjects after LHR administration. Their values were significantly higher than those observed during the control study. These data demonstrate sensitivity of the pituitary gonadotropes to synthetic LHR and a pubertal-type response to LH in the early hours of human life.