Gonadotropin secretion in girls with turner syndrome measured by an ultrasensitive immunochemiluminometric assay.

BACKGROUND/AIM: Gonadotropin levels measured by radioimmunoassays are high in girls with Turner syndrome (TS), but overlap significantly with those of normal girls. We hypothesized that gonadotropin levels would be above the normal range in TS when measured by ultrasensitive assays. METHODS: Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were measured in 68 TS, and 133 control girls using ultrasensitive immunochemiluminometric assays (ICMA). RESULTS: FSH levels in TS and normal girls were highest in early childhood (56.0 +/- 39.7 and 2.3 +/- 1.8 IU/l, respectively), declined at 6-10 years of age (11.3 +/- 13.1 and 1.8 +/- 0.9 IU/l, respectively), and then increased again (104.4 +/- 68.9 and 4.9 +/- 2.4 IU/l, respectively). FSH was in the normal range on 11 of 27 occasions in TS girls with ages 5-10 years, and on 3 of 44 occasions in >10 years. Although average LH values were higher than those of controls, they often overlapped the normal range. CONCLUSION: A significant number of TS girls have normal gonadotropins by ICMA. Spontaneous gonadotropin levels are not an adequate screening test for the diagnosis of TS but may prove useful for predicting the gonadal function and determining the appropriate timing of estrogen replacement therapy.

Development and validation of radioligand binding assays to measure total, IgA, IgE, IgG, and IgM insulin antibodies in human serum.

Radioligand binding assays for total and Ig classes of insulin antibodies (IAB) were developed and validated. For each assay, insulin-extracted serum samples were incubated with radiolabeled insulin in the presence and absence of high levels of unlabeled insulin to determine nonspecific binding and total binding, respectively. To measure total IAB, antibody-bound insulin was precipitated with a polyethylene glycol solution, washed, and counted in a gamma-counter. To measure IgG IAB, samples were treated with protein G-Sepharose beads, centrifuged, washed, and counted. For the measurement of IgA, IgE, and IgM IAB, IgG was removed from the samples and treated with anti-IgA, -IgE, or -IgM conjugated to Sepharose beads, centrifuged, washed, and counted. The acid/charcoal extraction of bound and unbound insulin from serum samples was optimized. Specificity and binding capacity of the protein G and antibody-bound beads were evaluated and optimized. The linear region of the total and IgG IAB assays was determined using serum samples containing high levels of insulin antibodies. The limit of quantitation, limit of detection, and precision for all the assays were also determined.