The Proximate Determinants of Fertility in Populations Exposed to Chronic Hypoxia

Vitzthum, Virginia J.; Wiley, Andrea S.

doi:10.1089/152702903322022758

Cited by 54 publications

(28 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It has been suggested that hypobaric hypoxia reduces fertility in humans. Nonetheless, epidemiological studies of high and low altitude populations have not been able to verify this proposal [2]. Based on the hormonal changes observed in men and rats at high altitude, some authors have proposed that CHH affects the hypothalamic/gonad axis (e.g.…”

mentioning

confidence: 99%

Time Course of Endocrine Changes in the Hypophysis-Gonad Axis Induced by Hypobaric Hypoxia in Male Rats

et al. 2008

View full text Add to dashboard Cite

Abstract. Chronic hypobaric hypoxia (CHH) induces a decrease in sperm output and spermatogenesis in male rats. The mechanisms that underlie these changes in testicular function are unknown and could involve changes in the hypophysis-gonad axis. We have tested the hypothesis that changes take place in the endocrine status (FSH, follicle stimulating hormone; LH, luteinizing hormone; testosterone) of rats subjected to CHH. Male Wistar rats were maintained under normobaric or hypobaric conditions (428 torr, 4,600 m). On days 0, 5, 15 and 30 post-exposure, 12 rats were anesthetized, their body weights were measured and blood samples were collected. The testicles were fixed in 4% formaldehyde and processed for histological analysis. In this time course, the FSH levels rose by day 5 post-exposure. On subsequent days, the FSH levels decreased in rats subjected to CHH with a tendency to remain higher than the normoxic group. The LH plasma levels decreased in rats exposed to CHH. Consistent with the decrease in LH levels, the plasma testosterone level decreased significantly after 30 days of CHH exposure. Integrated analysis of hormonal changes in rats subjected to CHH and the body dehydration that occurs in HH allows us to conclude that the effects of CHH on spermatogenesis may be partially related to changes in the hypophysis-gonad hormonal axis. Key words: Fertility, High altitude, Hypobaric hypoxia, Testicular function, Testis (J. Reprod. Dev. 54: [18][19][20][21] 2008) hronic hypobaric hypoxia (CHH) is experienced by an increasing number of sea level natives exposed to high altitude because of tourism, border patrol, mining or rural health and education activities [1]. It has been suggested that hypobaric hypoxia reduces fertility in humans. Nonetheless, epidemiological studies of high and low altitude populations have not been able to verify this proposal [2]. Based on the hormonal changes observed in men and rats at high altitude, some authors have proposed that CHH affects the hypothalamic/gonad axis (e.g. [3][4][5]). However, the results in the literature have been controversial. Nelson et al. reported that the plasma levels of GH, LH, FSH and TSH of hypoxic rats did not differ from the control values [3]. These results are in agreement with the reported absence of changes in the testosterone levels of rats exposed to hypoxia compared with sea level controls published by Gonzales et al. [5]. Instead, Sawhaney et al. [4] reported a decrease in the LH and testosterone levels in men exposed to CHH. Exposure of male rats to chronic hypobaric hypoxia and intermittent hypobaric hypoxia induced evident changes in testicular morphology [6][7][8][9], strong metabolic stress and loss of spermatogenic cells [8]. Local changes observed in testicles exposed to hypoxia include neovascularization and an increase in temperature. Thus, local changes that could lead to the observed effects on spermatogenesis do occur. However, it is highly likely that these local changes are also accompanied by changes in the hypophysis-gon...

show abstract

mentioning

confidence: 99%

Time Course of Endocrine Changes in the Hypophysis-Gonad Axis Induced by Hypobaric Hypoxia in Male Rats

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Although it has been proposed that hypoxia reduces fertility (number of live births), the complex interplay of behavioral and sociocultural factors that underlie fertility appear to exert the predominant effect at high altitude [ 1 ]. Historical observations in the Andean region raised the question whether hypoxia reduces fertility through impairing fecundity (the ability to conceive) and/or by increasing fetal loss, especially in newcomers to high altitude [ 2 ].…”

Section: Fertilitymentioning

confidence: 99%

“…Recent data from the Peruvian National Institute of Statistics and Informatics (INEI 2001) report a global fecundity rate of 3.7 (the number of expected births through a woman's reproductive period, having children at the prevailing rate for each age) for altitudes >2,000 m compared to 2.4-3.8 in sea level and jungle zones [ 5 ]. Estimates of completed fertility from Himalayan populations range from 3.2 to 7.4 [ 1 ].…”

Section: Fertilitymentioning

confidence: 99%

Reproduction and Growth

Niermeyer

2013

High Altitude

View full text Add to dashboard Cite

Reproduction and development during infancy and childhood present critical, vulnerable periods in the individual lifecycle and the health of a population. For humans living permanently at high altitude, the environment they inhabit adds risks for maternal and child health and survival. In addition to hypoxia, many high-altitude regions impose other constraints on the circumstances necessary for optimal fetal development and infant/child survival. These include impoverished living conditions, social inequalities, physically demanding livelihoods, nutritional defi ciencies, and infectious diseases. Such determinants infl uence fertility, fetal loss and growth, neonatal survival, and child development. Populations resident at high altitude for millennia, for example the Tibetans in the Himalaya and the Aymara and Quechua of South America, attest to possibility of not only surviving but also thriving, Hypoxia, as well as other environmental and social factors, shapes reproduction and fetal/infant growth at high altitude. Although fertility and early fetal loss differ little from patterns observed at lower altitude, placental development does differ and the medical complications of pre-eclampsia and post-partum hemorrhage pose greater risks at altitude. Reduction in birth weight with increasing altitude of gestation occurs across high-altitude regions, resulting in an increased proportion of lowbirth-weight infants (<2,500 g). However, the magnitude of reduction in fetal growth varies among population groups, depending on maternal ventilation, plasma volume expansion, blood fl ow to the uteroplacental circulation, and nutrient transport. Neonatal, infant, and child mortality are increased at high altitude. Respiratory problems account for the majority of neonatal and infant deaths. Exposure to hypoxia during the fetal and neonatal periods may have consequences that extend into adult life and span generations.

show abstract

“…High altitude hypoxia (hypobaric hypoxia, HH) is said to reduces fertility in humans (Farias et al, 2005a;Cikutovic et al, 2009;Hwang et al, 2009;Gat et al, 2010aGat et al, , 2010b. However, epidemiological studies of high and low altitude populations did not support this hypothesis (Vitzthum & Wiley, 2003;Bartsch et al, 2004). In previous publications, it was shown that the exposure of male rats to continuous chronic hypobaric hypoxia and intermittent chronic hypobaric hypoxia induced evident changes in testicular morphology, arrest of spermatogenesis and other metabolic changes related to lipid peroxidation (Farias et al, 2005a).…”

Section: Introductionmentioning

confidence: 99%

Reversible Effect of High Altitude on Rat Testis Morphology and Spermatogenesis: Histological and Ultrastructural Study

et al. 2016

View full text Add to dashboard Cite

SUMMARY:The study was carried out at two different altitudes in the southern region of Saudi Arabia: Abha, 2,800 meters above sea level, the high altitude (HA) area and Jazan, 40 meters above sea level the low altitude (LA) area. Following exposure to high altitude, testes of rats revealed various types of atrophy and degeneration in the seminiferous tubules and in the interstitial tissue. There was detachment of the basal laminae of the tubules and a profound decrease in cellularity. When rats were brought back to their habitat (LA) and later examined, many tubules showed normal population of cells including spermatids and spermatozoa. Well-arranged epithelium was seen in most of the seminiferous tubules of these animals, normal interstitial space and no detachment of the basal lamina. Apparently complete recovery had been achieved ultrastructurally, in hypoxic group; some spermatogenic cells lost their normal architecture, being irregular in shape with some features of necrosis, such as shrinkage and pyknotic nuclei characterized by chromatin condensation. Significant decrease in epithelial height was noticed in these animals (P <0.05). Also, the diameter of the tubules showed slight decrease with concomitant increase in interstitial spaces.

show abstract

The Proximate Determinants of Fertility in Populations Exposed to Chronic Hypoxia

Cited by 54 publications

References 59 publications

Time Course of Endocrine Changes in the Hypophysis-Gonad Axis Induced by Hypobaric Hypoxia in Male Rats

Time Course of Endocrine Changes in the Hypophysis-Gonad Axis Induced by Hypobaric Hypoxia in Male Rats

Reproduction and Growth

Reversible Effect of High Altitude on Rat Testis Morphology and Spermatogenesis: Histological and Ultrastructural Study

Contact Info

Product

Resources

About