Kyung N H, Barkan A, Klibanski A, Badger T M, McArthur J W, Axelrod L, Beitins I Z
J Clin Endocrinol Metab. 1985 May;60(5):827-35. doi: 10.1210/jcem-60-5-827.
We previously demonstrated that during a 10-day fast in mildly obese men, urinary gonadotropin excretion significantly increased, and serum testosterone concentrations significantly decreased. The mechanisms by which these changes occur are unknown. We postulated that the mechanism of the gonadotropinuria might involve decreased proximal renal tubular reabsorption of gonadotropins during fasting and might be related to renal tubular reabsorption of ketones during fasting, a process that is enhanced by carbohydrate (CHO) administration. We studied the effects of CHO supplementation on ketosis, ketonuria, and reproductive hormone secretion and excretion in 14 mildly obese men, 24-54 yr old, who were 14-69% above ideal body weight. Group I (n = 6) received no CHO supplementation, group II (n = 4) received 15 g CHO, and group III (n = 4) received 45 g CHO daily during the 10-day fast (F). During the control (C) and refeeding (R) periods, all subjects received a 1500-cal diet. Daily 24-h urine collections were made for the measurement of total ketones (millimolar concentrations) and LH and FSH (expressed as international units of the Second International Reference Preparation of human menopausal gonadotropin). Values (mean +/- SE) for 3 representative days (control day 3, fasting day 8, and refeeding day 3) for all subjects are shown below: (table; see text) We also studied the effects of CHO supplementation on serum levels of pituitary gonadotropins, LH and FSH responses to exogenous LHRH stimulation, biological activity of LH, and circulating total and free testosterone levels. Neither dose of CHO prevented the decline in total and free testosterone levels. Serum LH concentrations, as measured by both the RIA and in vitro bioassay did not change significantly with fasting. Serum FSH concentrations in daily samples did not change significantly. The previously reported decline in the FSH response to LHRH stimulation with fasting was not prevented by CHO. We conclude that CHO supplementation prevents the gonadotropinuria of fasting in men. The effect appears to occur in the kidney. The mechanisms may be related to that by which CHO promotes the renal tubular reabsorption of ketones. The reduced serum testosterone level cannot be explained by a lack of biologically active LH. It appears that fasting has a direct effect on the testis, possibly by reducing its responsiveness to gonadotropic stimulation or by inhibiting steroidogenesis.
我们之前证明，在轻度肥胖男性为期10天的禁食期间，尿促性腺激素排泄显著增加，血清睾酮浓度显著降低。这些变化发生的机制尚不清楚。我们推测，促性腺激素尿的机制可能涉及禁食期间近端肾小管对促性腺激素的重吸收减少，并且可能与禁食期间肾小管对酮的重吸收有关，碳水化合物（CHO）给药可增强这一过程。我们研究了补充CHO对14名年龄在24至54岁、超出理想体重14%至69%的轻度肥胖男性的酮血症、酮尿症以及生殖激素分泌和排泄的影响。第一组（n = 6）未补充CHO，第二组（n = 4）每天补充15 g CHO，第三组（n = 4）在为期10天的禁食（F）期间每天补充45 g CHO。在对照（C）期和再喂养（R）期，所有受试者均接受1500卡路里的饮食。每天收集24小时尿液，用于测量总酮（毫摩尔浓度）以及LH和FSH（以人绝经期促性腺激素第二国际参考制剂的国际单位表示）。所有受试者3个代表性日子（对照第3天、禁食第8天和再喂养第3天）的值（平均值±标准误）如下所示：（表格；见正文）我们还研究了补充CHO对垂体促性腺激素血清水平、LH和FSH对外源性LHRH刺激的反应、LH的生物活性以及循环总睾酮和游离睾酮水平的影响。两种剂量的CHO均未阻止总睾酮和游离睾酮水平的下降。通过放射免疫分析（RIA）和体外生物测定法测得的血清LH浓度在禁食期间没有显著变化。每日样本中的血清FSH浓度也没有显著变化。之前报道的禁食时FSH对LHRH刺激反应的下降未被CHO阻止。我们得出结论，补充CHO可预防男性禁食时的促性腺激素尿。这种作用似乎发生在肾脏。其机制可能与CHO促进肾小管对酮的重吸收的机制有关。血清睾酮水平降低不能用缺乏生物活性的LH来解释。似乎禁食对睾丸有直接影响，可能是通过降低其对促性腺激素刺激的反应性或抑制类固醇生成。
