Patients with isolated gonadotropin deficiency were studied to determine whether pulsatile low dose gonadotropin-releasing hormone (GnRH) could induce the hormonal changes seen during normal puberty. Four male and two female patients with immature responses to a standard GnRH test (2.5 micrograms/kg) were given GnRH (0.025 micrograms/kg) iv every 2 h for 5 days. FSH responses varied between the sexes, and FSH concentrations in males rose continuously to 17.2 +/- 4.7 mIU/ml on day 5. In the females, FSH peaked at 13.8 and 15.8 mIU/ml on days 3-4 and then declined. The males showed increasing and the females decreasing incremental FSH responses to GnRH. LH concentrations and incremental responses to GnRH rose throughout the study in both sexes. Plasma testosterone rose slightly in the males to 0.7 +/- 0.2 ng/ml (P < 0.05), but in females estradiol increased to follicular range concentrations of 128 and 102 pg/ml. Standard GnRh tests on day 6 revealed maturation of gonadotropin responses in all patients. After termination of pulsatile GnRH, four patients were given single low dose GnRH injections on two to seven occasions over a period of 2-32 days. Initial LH responses were 2- to 14-fold greater than those seen on day 5 of pulsatile GnRH, and decreased over the next 3 weeks. FSH responses showed less initial augmentation and declined more slowly. Low dose pulsatile administration of GnRH to patients with isolated gonadotropin deficiency results in changing patterns of hormone secretion similar to those seen during puberty. Exaggerated pituitary sensitivity to GnRH may be present long after a brief period of GnRH stimulation, and may indicate previous rather than current secretion of GnRH.

A specific and sensitive homologous radioimmunoassay (RIA) for determination of hamster prolactin is described and compared to heterologous hamster prolactin RIA and to the homologous and heterologous RIAs for rat prolactin. With this method, we have determined that, in the golden hamster, diurnal plasma prolactin fluctuations have a mean interpeak interval of 1.5 h, that serum prolactin concentrations are influenced by day length, by ether vapors, by animal’s gender, and by refeeding following a fast but not by neurosurgical procedures which increase somatic growth and serum GH concentration in adult hamsters. Variations in day length influenced pituitary prolactin content and concentration, and pituitary removal abolished prolactin secretory responses to ether stress. A heterologous RIA for hamster prolactin which utilizes radioiodinated rat prolactin and rabbit antihamster prolactin serum (RK1–15) represents the most advantageous method for the measurement of hamster prolactin because of its high sensitivity (0.14 ng/ml), high antiserum binding to iodinated rat prolactin, and the ability to measure both hamster and rat prolactin.

Type 1A diabetes (T1D) is believed to be caused by immune-mediated destruction of β-cells, but the immunological basis for T1D remains controversial. Microbial diversity promotes the maturation and activation of certain immune subsets, including CD161bright CD8+ mucosal associated invariant T (MAIT) cells, and alterations in gut mucosal responses have been reported in type 1 diabetics (T1Ds). We analyzed T cell populations in peripheral blood leukocytes from juvenile T1Ds and healthy controls. We found that proportion and absolute number of MAIT cells were similar between T1Ds and controls. Furthermore, while MAIT cell proportions increased with age among healthy controls, this trend was not observed among long-standing T1Ds. Additionally, the CD27- MAIT cell subset is significantly increased in T1Ds and positively correlated with HbA1c levels. However, after T1Ds are stratified by age, the younger group has significantly increased proportions of CD27- MAIT cells compared to age-matched controls, and this proportional increase appears to be independent of HbA1c levels. Finally, we analyzed function of the CD27- MAIT cells and observed that IL-17A production is increased in CD27- compared to CD27+ MAIT cells. Overall, our data reveal disparate MAIT cell dynamics between T1Ds and controls, as well as signs of increased MAIT cell activation in T1Ds. These changes may be linked to hyperglycemia and increased mucosal challenge among T1Ds.

Type 1 diabetes (T1D) is a chronic disease characterized by autoimmune-mediated destruction of pancreatic insulin-producing beta cells. Interleukin (IL)-18 is a pro-inflammatory cytokine implicated in the pathogenesis of a number of inflammatory diseases. Here, we analyzed IL-18 levels in the plasma of juveniles with T1D. Compared to control subjects, IL-18 levels were significantly elevated in patients with T1D. On the other hand, levels of IL-18 binding protein (IL-18BP) and IL-37, two negative regulators of IL-18 function, remained unchanged when comparing T1D to control samples. Notably, however, although IL-18BP levels were not elevated, IL-18 and IL-18BP were found to be positively correlated in type 1 diabetics. Even so, free, unbound IL-18 remained significantly increased in diabetic patients. Additionally, correlation studies also revealed that IL-18 and IL-18BP are positively correlated with HbA1c levels in T1D patients, suggesting a potential link between IL-18 and metabolic control in these patients. Finally, we observed a significant increase in IL-18 protein expression within human pancreatic islet specimens collected from type 1 diabetics. These results further expand our knowledge of the role of IL-18 in T1D, may give insight into common pathogenic mechanisms associated with metabolic control in both T1D and T2D, and suggest that targeting this cytokine may improve therapeutic outcomes for T1D patients.

SummaryFourteen children between 2.5 and 16 years of age were studied to provide a quantitative estimate of the changes in gonadotropinreleasing hormone (GnRH) pulse amplitude in hypophysial portal plasma during puberty. Responses to physiologic doses of synthetic GnRH were measured [induced luteinizing hormone (ALH) and induced follicle-stimulating hormone (AFSH)] and compared with spontaneous fluctuations in gonadotropins [spontaneous luteinizing hormone (A.LH) and spontaneous follicle-stimulating hormone (A.FSH)I. One to four lowdose (0.0125 or 0.025 &kg IV) pulses of GnRH were given every 2 hr between OSOO and 1600 or 2200 and 0400 hr. Maximal peripheral plasma concentrations of GnRH one min after pulses averaged 107 f 25 pg/ml (S.E.) (0.0125 pg/ kg dose) and 218 * 33 pg/ml (0.025 &kg dose). In early pubertal children,the maximal ALH was similar to or less than the maximal nocturnal L L H (maximum, ALH 7.0 f 0.2 versus maximum A.LH 7.0 * 1.3 mIU/ml in boys, 7.0 f 1.2 versus 16.0 f 3.0 mIU/ml in girls). Luteinizing hormone (LH) responses were low or undetectable in children whose bone ages were less than 10 years. When discernible, LH pulse frequency was similar during daytime and nighttime sampling periods in early pubertal boys. However, two hourly injections of GnRH given during the day did not simulate the initial nocturnal rise in LH. Overall mean AFSH and L F S H that luteinizing hormone (LH), but not follicle-stimulating hormone (FSH) release increases strikingly at puberty in both sexes, whereas FSH release is greater in prepubertal girls than boys.Information about GnRH secretion into the hypophysial portal system has been obtained via direct measurement in several animal species (1,3,6,18,22). Camel et al. (3) have measured portal blood GnRH in monkeys and found it to vary between 10 to 800 pg/ml. In humans, suchmeasurements are impractical, and information has been obtained via indirect techniques. We have pre-viously used responses to synthetic GnRH to istimate the hypophysial portal plasma concentration of GnRH in men and to gain information about its secretory pattern. On the basis of these studies, we concluded that the portal plasma concentration of GnRH varied between <30 and 300 pg/ml (a), an estimate similar to those obtained by direct measurement in animals. A similar study in prepubertal children would be difficult to interpret because of the shallow dose response curve for LH in these children (7,9). In this study, we have utilized the striking FSH responses of prepubertal and hypogonadal children, as well as the marked day/night difference in LH secretion characteristic of early puberty to estimate GnRH pulse amplitude. MATERIALS AND METHODSwere similar in three prepubertal female patients (3.0 * 0.2 versus 2.8 * 0.2 mIU/ml). AFSH was greater than L F S H in two patients All studies were done in the Clinical Research Center after with gonadal dysgenesis (bone ages, 2.5 m d 5 years) m d in one written informed parental These studies were approved by the Human Investigation Committee of t...