Effect of octreotide on 24-hour growth hormone and prolactin secretory patterns in acromegalics

The relationship between serum levels of prolactin and growth hormone in the early postnatal period

BackgroundIn the neonatal period, the pituitary hormones including prolactin (PRL) and human growth hormone (hGH) are secreted in high amounts due to immature feedback mechanisms. As both hormones are secreted in part by the same somatomammotrophic cells, we investigated their relationship in newborns with respect to sex, gestational week, method of delivery, and anthropometric data.MethodsThe serum levels of PRL and hGH were measured in blood drawn from 225 newborns. The newborn data were extracted from medical records.ResultsA positive correlation was found between log-transformations of PRL and hGH (r=0.17; P=0.01; n=225), with a stronger correlation in newborns whose blood samples were taken more than 2 days after birth (r=0.42; P<0.001; n=130). Log-transformations of the PRL/hGH ratio demonstrated a positive correlation with the gestational week (r=0.39; P<0.001; n=200). Multiple regression analysis showed that 15% of the variance in the logarithm of this ratio is attributed to the gestational week.ConclusionIn newborns, serum PRL and hGH levels show a positive correlation that can be explained by common regulatory factors or a drift phenomenon. A higher gestational week is associated with a higher PRL/hGH ratio. Further studies are needed to look for possible confounders and to determine the PRL-hGH relationship in different conditions.

Two types of growth hormone rhythm in boys with constitutional short stature

The relationship between temporal and quantitative changes in pulsatile growth hormone (GH) secretion and growth of constitutionally short children (CSS) was studied in 19 prepubertal boys and 4 with early adrenarche aged 7.8 to 14 years. Continuous plasma GH monitoring was performed at 30 minutes intervals during 24 hours. The data were analysed by single and serial best fit (BFT) cosinor analysis for rhythm parameters and the Pulsar peak detection program for determining pulsatile properties. The pulsatile patterns were expressed in mean GH concentration, area under the curve, mean pulse area and maximal pulse height but not in the number of pulses. Thirteen out of 23 patterns exhibited significant 24-h compatible rhythms. The studied cohort was divided into two groups, those who exhibited the 24-h circadian rhythm (CIR) and those who lacked it (NCIR). Ultradian 2.5-4 h rhythms were observed in all patients. The NCIR children were significantly shorter than the CIR group (p = 0.017). The CIR boys secreted a significantly higher (p = 0.01) amount of GH during the 24-h span, most of which was during sleep. Our data indicate that the magnitude of pulses rather than their number is responsible for the quantitative differences observed between the two groups of boys with CSS. It is suggested that a lack of 24-h rhythmicity and the associated reduced nocturnal pulsatility play a role in the manifestation of short stature.