Reproductive hormones

It needs to be noted that a toxic effect on the reproductive system may be mediated through alterations in normal functions of the central nervous system, gonads (ovaries, testicles), or on the pharmacokinetics of reproductive hormones. ... 

In vivo studies in animals suggest that endosulfan may disrupt normal reproductive hormone levels in male animals, but that it is not an endocrine disrupter in females. Persistent depressed testicular testosterone was seen in male rats after intermediate duration oral exposures to endosulfan. In ovariectomized female rats, orally administered endosulfan did not induce normal development of female reproductive tissues, and in female mice and immature female rats, acute parenteral exposure to endosulfan did not affect several endocrine-related end points. In vitro studies have evaluated endosulfan for estrogen receptor (ER) and cytosolic protein binding affinity, ER-mediated reporter gene expression, estrogenic induction of cell proliferation, and alteration of relative abundance of active estradiol metabolites. Overall, in vitro evidence in favor of endosulfan estrogenicity indicates relatively weak potency compared to 17[3-estradiol. Apparently contradictory results were reported in different... 

The overall evidence indicates that endosulfan administered in vivo may be disruptive of reproductive hormone levels in male animals. On the other hand, endosulfan is neither estrogenic nor disruptive of thyroid or pituitary hormone levels in females in vivo, despite its weak estrogenicity in several in vitro test systems. 

There has been some speculation that estrogenic compounds may adversely affect the fertility of men by reducing testosterone levels and sperm counts (Atanassova et al, 2000). To date, however, the limited information available suggests that consumption of phytoestrogens does not affect reproductive hormones or semen quality (Nagata, 2000 Nagata et al., 2001 Mitchell et... 

Not specified Imperial College of Science, Technology and Medicine Lead and male reproductive function, evaluate impact of changes in indicators of semen quality and reproductive hormones as function of occupational lead exposure ILZRO... 

In permissiveness, one hormone enhances the responsiveness of the target tissue to a second hormone in other words, the first hormone increases the activity of the second. For example, the normal maturation of the reproductive system requires reproductive hormones from the hypothalamus, pituitary, and gonads as well as the presence of thyroid hormone. Although thyroid hormone by itself has no effect on the reproductive system, if it is absent the development of this system is delayed. Therefore, thyroid hormone is considered to have a permissive effect on the reproductive hormones, facilitating their actions causing sexual maturation. 

Sunscreens and their degradation metabolites analyzed in this study are potential inducers of the oestrogen (ER) and aryl hydrocarbon receptors (AhR, also known as Dioxin Receptor). Ectopic activation of these pathways can cause severe damage to organisms and their ecosystem by altering reproduction, hormonal and/or circulatory systems [73-75] as well as they have been associated with carcinogenic and mutagenic effects [76-78]. 

Figure 11.10 Interrelationships between various hormones regulating reproductive function in the male and female. Particular emphasis is placed upon the regulatory effect many have on the production levels of additional reproductive hormones...

Chapin RE, Norton RM, Popp JA, et al. 1982. The effects of 2,5-hexanedione on reproductive hormones and testicular enzyme activities in the F-344 rat. Toxicol Appl Pharmacol 62 262-272. 

Three dietary intervention studies reported the effects of soy or soy phytoestrogen consumption on reproductive hormones in men and very modest alterations of doubtful clinical significance were found (Habito et al., 2000 Nagata et al., 2001). None of these studies evaluated the prostate itself, and it is possible that soy consumption alters local hormone metabolism and action within the gland. 

Main KM, Mortensen GK, Kaleva MM, Boisen KA, Damgaard IN, Chellakooty M, Schmidt IM, Suomi AM, Virtanen HE, Petersen DV, Andersson AM, Toppari J, Skakkebaek NE (2006) Human breast milk contamination with phthalates and alterations of endogenous reproductive hormones in infants three months of age. Environ Health Perspect 114 270-276... 

Numerous studies have shown that reproductive hormones regulate skin gland activity. 

Raymer, J., Wiesler, D., Novotny, M., etal. (1986). Chemical scent constituents in urine of wolf Cams lupus) and their dependence on reproductive hormones. Journal of Chemical Ecology 12,297-314. 

The authors concluded that the mixture induced effects on the liver and the kidney, and on the general metabolism at high doses but caused only minor effects on immune function, reproductive hormone levels, or general indices of reproductive function measures. The results suggested that additive or synergistic effects of exposure to contaminants resulting in residue levels representative of contemporary human tissue levels are unlikely to result in adverse effects on immune function or reproductive physiology in male rats. 

Lactoferrin is the major whey protein present in breast milk (Teraguchi et ah, 1996) with many microbicidal properties (Leon-Sicairos et ah, 2006). The concentration of lactoferrin in milk has been reported as 1 g/liter in mature milk and 7 g/liter in colostrum (Houghton et ah, 1985). The concentration of lactoferrin in breast milk is controlled by the reproductive hormones prolactin and estrogen (Ward et ah, 2005). Lactoferrin has been demonstrated to resist digestion in the infant gut as it has been recovered intact from the stool of breast-fed infants (Bemt and Walker, 1999). Lactoferrin acts mainly in an iron-free state (apo-lactoferrin) and its microbicidal activity is reported to increase in proportion to its concentration in milk (Leon-Sicairos et ah, 2006). 

Willey, K. (1999). An elusive role for glycosylation in the structure and function of reproductive hormones. Hum. Reprod. Update 5(4), 330-335. 

Secondary to the societal concerns around chemical-related endocrine disruption, the OECD407 subacute 28-day toxicity study protocol has been updated in 2007 with parameters relating to endocrine homeostasis. Specifically, circulating thyroid hormones and detailed assessment of reproductive organ parameters were added to the protocol. Reproductive hormones were suggested as additional parameters but they were deemed not informative in view of their large variability in untreated animals. 

Degradation of Estrogens and Other Reproductive Hormones in the Environment... 

However, broadly steroids can be classified only in to two main classes sex or reproductive hormones and adrenocorticoid or adrenocortical hormones. 

Polybrominated Biphenyls. PBBs have the potential to interact with the endocrine system based on effects that mainly include changes in levels of thyroid and female reproductive hormones. No studies were located that investigated the estrogenic and antiestrogenic activity of PBBs in vitro or in vivo at the level of the estrogen receptor. 

Estrogen and Reproductive Hormones as Antidepressant Augmenting Agents... 

Other uses of the reproductive hormone approach are to avoid cyclical use of estrogen/progestins, eliminate progestins, add testosterone, or add dihydroepian-drosterone (DHEA). Such approaches remain anecdotal and require controlled studies of how they may be useful augmenting agents for antidepressants both in women and in men. 

Reproductive Hormones and Synaptogenesls Across the Menstrual Cycle... 

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