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The heterogeneity of serum PRL in a hyperprolactinemic but fertile woman (Patient A) was studied by gel chromatography. Ninety percent of her PRL eluted with the void volume as "big, big" PRL and only 6% coincided with monomeric "little" PRL. Sera from a woman who had hyperprolactinemia associated with infertility (Patient B) and a normal woman (Patient C) exhibited the usual heterogeneous distribution, where 5% and 19%, respectively, eluted as big, big PRL and 76% and 65%, respectively, eluted as little PRL. Serial dilutions of the serum from Patient A displayed nonparallelism to the lines obtained from similar dilutions of both PRL standard and serum from a normal woman, suggesting possible immunological differences among the three forms of the circulating hormone. This finding, together with reports that suggest big, big PRL has a low receptor affinity, may account for the apparent lack of any biological effect upon Patient A from her sustained hyperprolactinemia.

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Summary. The effects of rat growth hormone (1 ~tg/ ml) on the synthesis and release of insulin by isolated rat islets of Langerhans were studied. There was no effect of growth hormone on the release of insulin from freshly isolated islets during 30 min incubation periods. By contrast, islets previously cultured for 16h with growth hormone exhibited a 40% increase in the release of insulin in response to glucose or to glucose and theophylline. These islets also showed specific increases in basal and glucose-stimulated insulin synthesis of 16% and 21% respectively, together with a 22% increase in the basal rate of total protein synthesis. The total insulin content of islets was not affected by culture with growth hormone. The adenylate cyclase activity of islet homogenates was unaffected by the presence of growth hormone during 30 min incubations. When homogenates from islets previously cultured with growth hormone were studied, basal adenylate cyclase activity was unchanged, while fluoride-stimulated adenylate cyclase activity was increased by 37%. It is concluded that growth hormone can directly affect the synthesis and release of insulin in islets of Langerhans, without relation to its metabolic activities in other target organs.

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The purpose of this study was to determine whether elevation of plasma free fatty acids (FFA) in early pregnancy would cause alterations in insulin-stimulated glucose disposal similar to those occurring in late gestation. Seven glucose-tolerant women underwent 4-h euglycemic hyperinsulinemic (1 mU/kg.min) clamping during the early second trimester of pregnancy (14-17 weeks) on 2 consecutive days, receiving either lipid (Liposyn II; 1.5 mL/min) and heparin (0.4 U/kg.min; L/H) or saline/glycerol (2.25 g/h; S/G) infusions. Rates of total body glucose disposal (6,6-2H2 glucose) and of carbohydrate and fat oxidation (indirect calorimetry) were determined at hourly intervals. Blood glucose was clamped at about 85 mg/dL. Plasma FFA increased from 290 +/- 50 to 1000 +/- 139 mumol/L during L/H infusion and decreased from 351 +/- 60 to 35 +/- 11 mumol/L during S/G infusion. L/H infusion inhibited insulin stimulation of total body glucose disposal by 28% compared with S/G infusion (from 6.7 +/- 0.7 to 4.9 +/- 0.6 mg/kg.min; P < 0.01). L/H infusion increased fat oxidation from 0.73 +/- 0.04 to 1.26 +/- 0.2 mg/kg.min (P < 0.05) and decreased carbohydrate oxidation from 2.0 +/- 0.2 to 1.6 +/- 0.2 mg/kg.min (P < 0.05). Endogenous glucose production decreased equally by approximately 70% during L/H and S/G infusions. These data showed that elevating plasma FFA levels during early pregnancy inhibits total body glucose uptake and oxidation. We conclude that elevation of plasma FFA can contribute to the peripheral insulin resistance commonly observed during late pregnancy.

Summary. Serial measurements of serum progesterone, oestradiol, prolactin, human chorionic gonadotrophin (hCG) and human placental lactogen (hPL) have been determined in 32 healthy women at regular intervals throughout pregnancy. The data confirm previous reports that levels of these hormones vary widely between individuals at each stage of gestation, but further analyses have shown two other features: first there is a clear tendency for individuals to retain their rank in the spectrum of hormone values throughout pregnancy; second when the concentrations of the individual hormones (except hCG) are transformed to logarithmic values, the trends within individuals approximate well to straight lines during the second and third trimester of pregnancy. These findings provide a relatively simple method for describing the rates of change in the concentrations of these hormones and for examining possible relations between them. They also suggest that the quality of the maternal endocrine milieu may be determined at an early stage of gestation.