Byrd W, Bennett M J, Carr B R, Dong Y, Wians F, Rainey W
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235-9032, USA.
J Clin Endocrinol Metab. 1998 Aug;83(8):2849-54. doi: 10.1210/jcem.83.8.5008.
Inhibins are glycoprotein members of the transforming growth factor-beta family that have been implicated in the control of spermatogenesis by exerting a negative feedback on FSH secretion. In addition, locally produced inhibins may play a role in paracrine regulation of testicular function. Immunoassays were used to measure the two biologically active dimeric forms of inhibin (inhibin A and B) in serum, seminal plasma, and urine. To better define their actions, inhibins were measured in the male during infancy, sexual maturation, and senescence. Inhibin B but not A was measurable in the serum of male newborns, infants, children, and adults. In adult males, measurable levels of inhibin B were detected in the seminal plasma but not the urine. The circulating levels of inhibin B increased shortly after birth and peaked at 4-12 months of age (210 +/- 31 pg/mL). The concentration measured in the serum then decreased to a low of 81 +/- 12 pg/mL of inhibin B from 3-9 yr of age followed by a gradual increase beginning with the onset of puberty and reaching another peak of 167 +/- 20 pg/mL in males who were 20-30 yr of age. Inhibin B levels then gradually declined with increasing age up through 90 yr of age. Serum levels of gonadotropins and total testosterone production were also measured in these same males. There was a brief increase in the gonadotropins (FSH and LH) during the few months of postnatal development, followed by a decrease to basal levels until the onset of puberty at 10-14 yr of age. Testosterone was also increased in the serum of infants from day 1 through 12 months of age, which decreased in young children but increased again following the elevation of gonadotropins during puberty. In adults aged 20-90 yr, serum levels of inhibin B were inversely proportional to levels of FSH but not LH or testosterone. In males in which a semen analysis was performed, those males with normal semen analysis had a significantly higher inhibin B levels, sperm production, and lower FSH levels than males with either oligospermia or nonobstructive azoospermia. The levels of Inhibin B found in circulation were a good marker for testicular function and could be useful in the diagnosis of patients with semen abnormalities or a complete absence of spermatogenesis. Because this glycoprotein is secreted in high amounts in the prepubertal testis up to 3 yr of age, inhibin B could potentially be used as a marker in the diagnosis of cryptorchidism and precocious puberty.
抑制素是转化生长因子-β家族的糖蛋白成员，通过对促卵泡激素（FSH）分泌施加负反馈作用，参与精子发生的调控。此外，局部产生的抑制素可能在睾丸功能的旁分泌调节中发挥作用。采用免疫测定法检测血清、精浆和尿液中抑制素的两种生物活性二聚体形式（抑制素A和B）。为了更好地明确其作用，在男性的婴儿期、性成熟期和衰老期测定抑制素水平。在男性新生儿、婴儿、儿童和成人的血清中可检测到抑制素B，但未检测到抑制素A。在成年男性中，精浆中可检测到可测量水平的抑制素B，但尿液中未检测到。出生后不久，抑制素B的循环水平升高，并在4 - 12个月龄时达到峰值（210±31 pg/mL）。随后，3 - 9岁时血清中测得的抑制素B浓度降至低水平，为81±12 pg/mL，随后随着青春期开始逐渐升高，在20 - 30岁男性中达到另一个峰值，为167±20 pg/mL。此后，抑制素B水平随年龄增长逐渐下降，直至90岁。还对这些男性的促性腺激素血清水平和总睾酮生成量进行了测量。在出生后发育的几个月中，促性腺激素（FSH和LH）有短暂升高，随后降至基础水平，直至10 - 14岁青春期开始。婴儿从出生第1天到12个月龄时血清睾酮水平也升高，幼儿期下降，但在青春期促性腺激素升高后再次升高。在20 - 90岁的成年人中，血清抑制素B水平与FSH水平呈负相关，但与LH或睾酮水平无关。在进行精液分析的男性中，精液分析正常的男性其抑制素B水平显著高于少精子症或非梗阻性无精子症男性，精子生成量更高，FSH水平更低。循环中发现的抑制素B水平是睾丸功能的良好标志物，可用于诊断精液异常或完全无精子发生的患者。由于这种糖蛋白在3岁前的青春期前睾丸中大量分泌，抑制素B有可能用作隐睾症和性早熟诊断的标志物。
