Secreción de prolactina en hombres nativos de las grandes alturas / Prolactin secretion in high altitude natives

Objetivos: Determinar el efecto de la hipoxia crónica sobre la secreción de prolactina. Diseño: Estudio comparativo. Institución: Servicio de Endocrinología, Hospital Nacional Arzobispo Loayza, Lima, Perú. Participantes: Hombres jóvenes nativos de Lima y Cerro de Pasco. Intervenciones: Se estudió en forma dinámica tres grupos de hombres jóvenes normales de edad (X24a) y estado nutricional comparable, nativos de diferentes altitudes: 150 m.s.n.m. (Lima, N=10), 3 000 m.s.n.m. (Tarma, N= 10), 4 200 m.s.n.m. (Cerro de Pasco, n=11); y tres pacientes con mal de montaña crónico (MMC) nativos de Cerro de Pasco; todos clínicamente eutiroideos y sin bocio. En cada sujeto se determinó por RIA los niveles séricos basales de PRL y su respuesta. Principales medidas de resultados: Diferencia de niveles séricos de prolactina y su respuesta máxima a la hormona liberadora de tirotropina en sujetos a nivel del mar y en la altura. Resultados: Los niveles séricos basales de prolactina (PRL) y su respuesta máxima a la hormona liberadora de tirotropina (TRH) fueron significativamente menores en los nativos de altura en comparación con los del nivel del mar. La causa subyacente sería la hipoxia crónica, pudiendo estar implicados un incremento de la actividad dopaminérgica del sistema túbero û infundibular o una alteración a nivel del receptor o posreceptor del lactotrofo en los nativos de altura. Este hecho puede ser un mecanismo de adaptación para la conservación de la fertilidad en los hombres nativos de las grandes alturas. El escaso número de pacientes con mal de montaña crónico no permitió obtener resultados concluyentes, pero se observó persistencia de la menor secreción de prolactina, con una respuesta más tardía a la TRH. Se requiere más investigaciones en pacientes con MMC, para definir estas observaciones. Conclusiones: Los niveles séricos basales de prolactina y su respuesta máxima a la hormona liberadora de tirotropina fueron significativamente menores en los nativos de altura en comparación con los del nivel del mar.

Objectives: To determine the effect of chronic hypoxia on prolactin (PRL) secretion. Design: Comparative study. Setting: Endocrinology service, Hospital Nacional Arzobispo Loayza, Lima, Peru. Participants: Native young men from Lima and Cerro de Pasco. Interventions: Three groups of normal young men age (X24a) with comparable nutritional status, natives from different altitudes: 150 m.a.s.l. (Lima, N=10), 3 000 m.a.s.l. (Tarma, N= 10), 4 200 m.a.s.l. (Cerro de Pasco, n=11); and three patients with chronic mountain disease (CMD) natives from Cerro de Pasco were studied. All subjects were euthyroid and without goiter. RIA determinations of PRL basal serum levels and PRL response to thyrotrophin releasing hormone (TRH) 200 µg I.V. were carried out on each subject. Main outcome measures: Difference of serum prolactin levels and highest response to thyrotrophin releasing hormone in subjects at sea level and at high altitude. Results: Prolactin basal serum levels and the highest response to TRH were significatively less (P<0.05) in high altitude natives when compared to those at sea level. Underlying cause would be chronic hypoxia including either tubero-infundibular dopaminergic system activity increase or lactotrophsÆ receptor or post-receptor alteration in high altitude natives. This may be an adaptation mechanism for fertility preservation in high altitude natives. The few patients with chronic mountain disease studied did not allow concluding results, but persistence of less prolactin secretion was observed with late response to TRH. Further investigations in patients with MMD are required to define these observations. Conclusions: Prolactin basal serum levels and highest response to thyrotropin releasing hormone were significatively less in high altitude natives compared with those at sea level.

Secular change in growth of native children and adolescents at high altitude I. Puno, Peru (3800 meters).

A cross sectional sample of 969 native males from Puno (Peru), altitude 3800 m, ranging in age from 7-20 years, and studied for body height, weight, sitting height, leg length, and chest circumference in 1980, were compared, from the point of view of secular trend, with another cross sectional sample of 992 native males from the same place, which were investigated in 1945. In addition, similar observations were carried out in 1980, in a group of 112 females. The data indicate that in Puno there has been no secular increment in the adult body size. However for all ages between 7 and 19 years, body weight and height were significantly greater in 1980 than in 1945. This may be due to earlier sexual maturation in the present generation.

Serum inhibin is inversely correlated with serum FSH levels in adult men.

Serum inhibin, FSH, and testosterone levels were measured by radioimmunoassay in 36 normal human males, aged 8 to 63 years. Inhibin and FSH levels rose during 8 to 17 years to reach adult values. At these ages there is a significant direct linear correlation between serum FSH and inhibin levels (r = 0.81, p less than 0.01), whereas in adulthood the relationship between serum FSH and inhibin levels was significant inverse (r = -0.70, p less than 0.01). No correlation was found between serum testosterone and FSH (r = -0.18, p:NS) or between serum testosterone and inhibin (r = 0.14, p:NS). In senescence there is a significant decrease in the serum inhibin levels (r = -0.53, p less than 0.05). These findings suggest that negative feedback is established once serum inhibin has reached adult values, and that in physiologic conditions inhibin plays a greater role than testosterone in the negative feedback regulation of FSH.

The secretory activity of the seminal vesicles and its relationship to sperm motility: effects of infection in the male reproductive tract.

In 146 males aged between 20 years and 40 years attending an infertility service, the secretory activity of the seminal vesicles was assessed by measurement of corrected seminal fructose concentration. This value was related to the presence of a positive semen culture, other evidence of inflammatory processes in the reproductive tract and sperm motility. Only 48% of subjects with a positive semen culture showed evidence of inflammation in the reproductive tract, as assessed by the presence of more than 20 white blood cells per high power field, and greater than 10% spermagglutination in the ejaculate. There was a relationship between the inflammatory process, hypofunction of the seminal vesicles and poor sperm motility. When the semen culture was positive but there was no evidence of inflammation neither seminal vesicle function nor sperm motility was affected. When the semen culture was negative, i.e. no evidence of inflammation and the subjects were asthenozoospermic, the corrected fructose levels were normal. It is proposed that in these conditions the cause of asthenozoospermia may be factors other than accessory sex organ dysfunction. In conclusion, there was no close relationship between the bacteriological results and evidence of inflammation of the accessory glands. A positive semen culture was related to lower levels of corrected fructose (hypofunction of the seminal vesicles) when the positive sperm culture was associated with inflammation of the reproductive tract and asthenozoospermia.

Blood serotonin levels and male infertility.

Seventy men, aged 20-40 years, who were attending an infertility clinic were studied to evaluate associations between seminal quality, whole blood serotonin, and serum testosterone levels. Men with blood serotonin levels greater than 100 ng/ml showed lower sperm counts and sperm motility than those with normal levels of blood serotonin (less than 90 ng/ml). Seminal volume, pH, sperm morphology, fructose, citric acid, and serum testosterone values were similar between groups of patients with different levels of blood serotonin. The levels of blood serotonin correlated best with sperm motility when using a cubic regression analysis. When blood serotonin increased from 50 to 90 ng/ml (normal range), there was an increase in the percentage of spermatozoa with excellent motility. However, when serotonin was above 90 ng/ml the percentage of sperm with excellent motility decreased. An inverse exponential relationship was observed between blood serotonin and sperm count. The sperm count reached values of oligozoospermia when blood serotonin was over 100 ng/ml. It would appear that blood serotonin in the normal range is important for sperm motility. Values of serotonin above the normal range could affect negatively both sperm count and motility. These effects were observed in the absence of changes in serum testosterone levels.

Secular change in growth of native children and adolescents at high altitude Huancayo, Peru (3,280 meters).

Stature and weight of native children, adolescents, and adults at Huancayo , Peru (3,280 meters), were measured in 1977, 1978, and 1982 and compared with mean statures and weights reported in previous studies. The data indicate that in Huancayo there has been a secular increment in child stature, sitting height, and weight from 1937 to 1978-1982. The observed changes in stature are related to a proportionally greater increment in leg length relative to trunk length. It is concluded that the observed secular increase in body size reflects changes in the standard of living and a greater influx of nonnative populations, which are usually characterized by greater stature than natives.