Screening for gestational diabetes mellitus: can we be more efficient?

In a retrospective review of 471 patients screened for gestational diabetes mellitus (GDM) in a community laboratory, we compared 50 g polycose screening test results with those of the 75 g oral glucose tolerance test (GTT). The rate of GDM diagnosis was compared using criteria promulgated by the New Zealand Society for Study of Diabetes (NZSSD), Australian Diabetes in Pregnancy Society (ADIPS) and World Health Organisation (WHO). In those with borderline screening results (7.8-8 mmol/L) the rate of GDM diagnosis using NZSSD criteria was low (2.8%) compared with higher screening test results (> or = 8.1 mmol/L), where the rate was 7.4%. Corresponding rates were 7.5% and 13.5% using ADIPS criteria and 5.6% and 12.4% using WHO criteria. The predictive value of a positive 50 g screening test is therefore low, especially for the higher New Zealand criteria. In women with borderline screening results no subject had a two-hour plasma glucose of 9.0 mmol/L or more on oral GTT. This suggests that the current screening cut-off of 7.8 mmol/L might be raised to 8.1 mmol/L, resulting in a 25% reduction in the number of glucose tolerance tests. Those with significant risk factors such as macrosomia, however, still warrant greater clinical suspicion and closer follow-up.

ACTH immunoactivity in normal rat tissues: modulation by hypophysectomy and adrenalectomy.

This study investigates the effect of pertubation of the normal pituitary-adrenal axis on concentrations of adrenocorticotropin (ACTH)-like immunoactivity in peripheral tissues. We used a polyclonal antibody (West antibody) to measure ACTH-like immunoactivity in glacial acetic acid extracts of five tissues in adult male rats at increasing times (1, 7, 14, and 28 days) after hypophysectomy or adrenalectomy, and in normal control rats. Concentrations of ACTH-like immunoactivity were similar to those previously reported in liver, colon, heart, and small intestine and were not significantly affected by either hypophysectomy or adrenalectomy. While hypophysectomy also had no effect in the kidney, adrenalectomy resulted in a four-fold increase in extractable immunoactivity, first noticeable at seven days (p less than 0.005), but increasing progressively to 28 days (p less than 0.0005). Gel filtration showed that most of the increase in activity in kidneys of adrenalectomized rats corresponded to the 4.5 kD form comprising most of the serum ACTH immunoactivity and suggesting that the activity increase in kidney was largely due to ACTH derived from blood.

Inability to demonstrate an ultrashort loop feedback mechanism for luteinizing hormone in humans.

hCG has biological properties similar to those of LH, but can be measured separately from LH by current radioimmunometric assays. To investigate the possible existence of an autoregulatory mechanism for LH in humans, we compared the basal LH concentrations and the LH response to a GnRH stimulus with and without prior administration of hCG. On two separate occasions, at least 1 week apart, six normal (eugonadal) males and six normal postmenopausal females were given, in random order, either 10,000 IU hCG or saline followed by iv injection of a 200-micrograms bolus of GnRH. Blood samples were then taken 30, 60, 90, 120, 180, 240, and 300 min after GnRH. Serum concentrations of LH and hCG were measured at each time by two monoclonal antibody sandwich assays developed in our laboratory. After exogenous hCG, serum hCG concentrations rose rapidly to 200-500 IU/L (15,000-35,000 pg/mL) in both the men and women, remaining at this high level throughout the study. In the men, sex steroid concentrations did not change in response to the hCG during the 9 study hours. Compared to saline-treated controls, hCG had no significant effect in either men or postmenopausal women on the basal LH concentration or the response to a GnRH bolus, as determined by peak response and area under the LH/time curve between 0-300 min after GnRH. We conclude that an ultrashort loop feedback mechanism for LH on its own secretion does not exist in humans, as assessed by the present protocol.

Growth hormone-like material in normal human tissues.

We report herein the presence of extractable levels of immunoassayable (RIA) and receptor-assayable human GH (hGH)-like material in normal human liver, kidney, lung, striated muscle, colon, stomach, and brain. Levels of hGH by RIA were the highest in the liver (mean, 14.7 ng/g), followed by those in the kidney (mean, 11.3 ng/g) and lung (mean, 4.6 ng/g), but small amounts were detected in at least some specimens of all types of tissue. This material eluted in the region of monomeric pituitary hGH on Sephadex G-100 chromatography and showed parallelism in a RIA to pituitary hGH on log-logit plots of dose-response lines. Passage of the material through an anti-hGH immunocolumn greatly reduced its immunoreactivity. Assay of eight sets of extracts by receptor assay using a male rat liver membrane preparation showed the GH-like substance to have a receptor to immunoassay potency ratio of 3.8:1 relative to monomeric hGH standard. Scrupulous correction for acidity, osmolality, and possible protein and enzyme effects and extraction of the hGH-like material by immunoabsorption excluded the possibility of artifacts causing the appearance of hGH-like material in the extracts.