Gender-related differences in gastric emptying.

TO THE EDITOR: We have readwith interestthe articleby Data et al. (1) on gender-related differences in gastric emptying (GE). Their data, in fact, coincides with studies we published several years ago (2,3), despite variations in the method; as is usual among groups who investigate GE. The magnitude of the difference between males and females found by Data, expressed in terms of Tl/2 is almost identical to that we described (3); Tl/2 is 1.4 to 1.5 times more prolonged in females than in males. These results are also similar to those reported recently by Hutson et al. (4). In our work (3) we studied 18 women, the ages ranged from 18 to 27 yr, with a mean of 23 yr, who did not take contraceptives for the previous 6 mo, and all the studies were performed in the afternoon. We found a relationship between GE and the phase of the menstrual cycle, with a significant tendency to a faster GE in the ovular phase. There was no difference between the follicular and luteal phases. This find ing has not been confirmed by Horowitz et al. (5), studying ten women with a wider age range (from 26 to 45 yr, with a mean of 36 yr), who had bilateral ovarian tubal ligation performedfrom 6 to 120 mo previously. All the studies were performed in the morning. In this study no differences was noted between the follicular and luteal phases, but the ovular period was not studied. However, there is a previous obser vation by McDonald (6) who describeda fasterGE ofa liquid meal during ovulation. Unfortunately, in their study of 15 women aged from 23 to 44 yr, with a mean of 32 yr. Dali et al. do not inform us of the phase of the subjects' menstrual cycle. The day of the menstrual cycle on which GE studies were done is necessary to ascertainthe importance of a progesteroneeffect on GE. Since circadian variations in GE have been observed (7), the time of the day in which the studies were performed is also relevant. Other facts that can influence GE and should be mentioned are: dietary habits of the population studied (8), fast duration (9), degree of physical activity (10), and smokinghabit (11). Early studies to investigate possible differences in GE be tween sexesprobably faileddue to technical insufficiencies, for example, fractionate liquid aspiration at 10 and 20 mm only (12). There are, however, several clinical facts in gastroin testinal pathology which suggest a hormonal influence on gastrointestinal motility, e.g., the apparition of gastroesopha geal reflux and biliary ectasis during pregnancy. Furthermore, sexual receptors in the stomach and gastrointestinal tract of the baboon and cobaya have been recently identified (13,14). We agree with Data et al. in the sense that differences in GE between sexes are due to an effect of sex hormones on gastrointestinal motility. We believe that further studies are required to ascertain the influence of the phase of the men strual cycle, and probably of the hormonal situation related to age, on gastric motility. The exact adjustment to a monoexponential pattern in GE ofliquids is still controversial. GE ofliquids is often considered only to approximate an exponential model (15). In our study (3). such an exact adjustment to a monoexponential pattern was only possible in nine of 50 cases; in the remaining there was a better fit to a biphasic model, with a faster first phase followed by a stationary phase. This finding has also been described by other authors (16), and seems in agreement with the effect of gravity after ingestion (described by Hunt), with the passive escape of liquids to the duodenum before mixing with solids (1 7), and with the noninitiation ofthe gastric reflex of receptive relaxation when ingestion is <1 kg (18). GE studies using radiolabeledtest meals have contributed to the knowledge of the diversity of factors that influence gastric motility. We believe that with caution when deriving conclusions, radionuclide GE studies can still offer significant contributions to gastroenterology.