Offspring Human Fertility Behavior in Biodemographic Perspective (2003) / Chapter Skim
Currently Skimming:
5. Hormonal Mediation of Physiological and Behavioral Processes That Influence Fertility
5. Hormonal Mediation of Physiological and Behavioral Processes That Influence Fertility
Pages 104-139
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 104... ...
Understanding the changes in reproductive hormone secretion across the life span has implications for the design of biodemographic studies with regard to how and when reproductive function and sexual behavior are assessed and understanding the factors that influence these measures. Many lifestyle choices and life events can modulate activity of the reproductive axis and thus impact significantly on both reproductive physiology and behavior.
|
From page 105... ...
Even if reproductive hormone secretion is maintained, these life events can markedly alter circulating levels of reproductive hormones and thus influence fertility and sexual behavior. Biodemographic studies need to track lifestyle choices and life events to allow an accurate conceptualization of factors influencing fertility outcomes in human relationships.
|
From page 106... ...
For example, changes in both reproductive function and sexual behavior are commonly reported by patients suffering from depression, anxiety disorders, and obsessive-compuisive disorders (Clayton, 2002; Shabsigh et al., 2001~.
|
From page 107... ...
HORMONAL MEDIATION OF FERTILITY GABA CRH ,B-endorphin Glutamate NE NPY Testosterone\ ~ _ HYPOTHALAMUS \ GnRH I neuron ~ _\ PITUITARY LH and FSH A/ 107 /Progesterone I Estradiol / / FIGURE 5-1 Schematic diagram of the hypothalamic-pituitary-gonadal axis. Interrelationships between hormones and neurotransmitters are shown as stimulatory (+)
|
From page 108... ...
In the female, FSH acts on ovarian follicles to stimulate their growth and the production of estrogen. LH acts on the fully developed follicle to stimulate ovulation and then to support the function of the transient endocrine tissue formed during the last 2 weeks of each menstrual cycle, the corpus luteum (see Figure 5-2 for an overview of hormonal changes during the female menstrual cycle)
|
From page 109... ...
and FSH secretion are stimulated by GnRH, both hormones are released into the bloodstream in a puisatile manner, at rates of about one pulse every 2 to 3 hours in males and at rates that vary in females from one pulse every hour to one pulse every 8-12 hours at various stages of the menstrual cycle (Soules et al., 1984; see Figure 5-31. The puisatile nature of LH and FSH secretion can be a confound when hormone measures are collected as part of large population studies, in that a single blood sample may be collected when hormone levels are at the peak or nadir of a pulse; thus, variation
|
From page 110... ...
of the menstrual cycle. Steroid hormone levels on the day of each study are indicated on each graph.
|
From page 111... ...
steroid hormone concentrations in the blood, and it is important to distinguish between these. The gonadal steroid hormones have important actions in a number of reproductive tissues.
|
From page 112... ...
Steroid hormone secretion is relatively stable in the adult years in males, although it must be remembered that the gonadotropins and testosterone are secreted in a puisatile fashion. However, in the female there are marked changes in the circulating concentrations of gonadotropins and gonadal steroid hormones across the menstrual cycle (Erickson, 1978; Figure 5-2~.
|
From page 113... ...
Here we will not focus on detailed information about how each of these sexual behaviors is influenced by hormones but rather on two broad areas sexual desire and sexual behavior. There is evidence that most aspects of sexual behavior, particularly in males, are influenced by gonadal steroid hormones.
|
From page 114... ...
Androgen receptor mapping studies have shown considerable overlap in the distribution of androgen and estrogen receptors throughout the brain (Michael et al., 1995; Simerly et al., 1990~. Our discussion here will focus on the effects of gonadal steroid hormones on sexual behaviors, although there is evidence that they modulate a variety of other behaviors (Cameron, 2001~.
|
From page 115... ...
Estrogen replacement in ovariectomized female monkeys has been shown to increase female initiation of sexual behavior (Zehr et al., 1998~. At menopause, when there is a naturally occurring decrease in reproductive hormone levels (both estrogens and androgens)
|
From page 116... ...
Thus, although hormones are not necessary for female sexual behavior, there is accumulating evidence that hormones modulate sexual desire (Meston and Frolich, 2000; Wallen, 2001~. Further studies are needed to understand the differential roles of estrogens and androgens in this regard.
|
From page 117... ...
and defeminization of other tissues and functions (i.e., ovulatory competence, feminine sexual behaviors like lordosis, and other behaviors characteristic of females)
|
From page 118... ...
Sexual behavior is also dramatically increased in males at puberty, and there is a strong correlation at this
|
From page 119... ...
Moreover, there is evidence that social factors can be as important as hormonal factors in determining a girl's sexual behavior (U3ry et al., 1986~. Changes with Aging In males, testosterone levels decrease slightly with aging and there is a mean decrease in sexual behavior, although again there are large individual variations (Meston and Frohlich, 2000~.
|
From page 120... ...
It is also possible for exogenous steroid hormones to influence sexual behavior; however, these
|
From page 121... ...
and progesterone that provide increased negative feedback to the reproductive axis and thus decrease ovarian production of androgens could potentially decrease sexual drive in women. However, studies that have examined this have generally shown no effect of oral contraceptives on female sexual behavior (Meston and Frohlich, 2000~.
|
From page 122... ...
LIFE EVENTS THAT ALTER HORMONE LEVELS Life events that impact the functioning of the reproductive axis are often those that produce various forms of stress. Many physical forms of stress, including energy restriction, increased energy expenditure with exercise, temperature stress, infection, pain and injury, and psychosocial stress have been associated with suppression of reproductive hormone secretion and, if sustained, a suppression of fertility (Cameron, 1997, 1998; Lachelin and Yen, 1978; Pirke et al., 1989~.
|
From page 123... ...
Amenorrhea is often apparent for great lengths of time, with normal menstrual cycles sometimes returning when patients regain weight but often lasting long after weight recovery. Measurement of circulating levels of LH and FSH show that gonadotropin secretion during the weight loss phase of anorexia nervosa is very low and often nonpuisatile in nature or puisatile only during the nighttime period,
|
From page 124... ...
And brief periods of undernutrition have also been documented to decrease reproductive hormone secretion in humans (Cameron et al., 1991~. However, fertility would not be expected to be compromised during brief periods of undernutrition, particularly in females who seem to be somewhat protected from the effects of mild undernutrition in the follicular phase of the menstrual cycle, the period leading up to ovulation (Berga et al., 2001; Olson et al., 1995~.
|
From page 125... ...
The relatively few studies examining sexual behavior in women in the puerperium indicate that sexual interactions are relatively lower in the first few months after the birth of a child compared to prepregnancy levels (Alder et al., 1986; al Bustan et al., 1995; Byrd et al., 1998; Kayner and Zagar, 1983~. However, the reasons for the drop in frequency of intercourse are complex and include many factors other than hormonal changes, including fatigue, episiotomy discomfort, vaginal bleeding, dyspareunia, insufficient lubrication, fears of awakening the infant or not hearing the infant, and a decreased sense of attractiveness.
|
From page 126... ...
Treatment of these patients with cognitive behavioral therapy or with drugs that reduce the activity of some central neural systems activated by stress can restore fertility, although not in all cases (Berga et al., 1991, 1997~. Although the majority of studies examining the effects of psychosocial stress on reproduction have documented stress-induced suppression of reproductive function, there are a handful of human studies which have reported that girls who have grown up under conditions of family stress, such as an absent father in a home, with family conflict, a air!
|
From page 127... ...
In nonhuman primates a number chronic social stresses have been associated with a marked and sustained suppression of reproductive hormone secretion. These include prolonged restraint stress (Goncharov et al., 1984)
|
From page 128... ...
Many aspects of reproductive biology are difficult to study from the perspective of population biology approaches because of the great variation in function within an individual over a short course of time, such as with fluctuations in hormone levels over the menstrual cycle or even the fluctuation in reproductive hormone levels on an hour-to-hour basis. Biomedical approaches of studying individuals in more detail will be able to define relationships more clearly but are limited by the low power of examining relatively few individuals.
|
From page 129... ...
Manav 1995 Maternal sexuality during pregnancy and after childbirth in Muslim Kuwaiti women. Archives of Sexual Behavior 24:207-215.
|
From page 130... ...
Zumpe, and R.P. Michael 1978 Menstrual cycle influences on operant behavior of female rhesus monkeys.
|
From page 131... ...
Cameron, J.L., and C Nosbisch 1991 Slowing of pulsatile LH and testosterone secretion during short-term fasting in adult male rhesus monkeys (Macaca mulatta)
|
From page 132... ...
Bielert 1975 Female rhesus sexual behavior and distance to a male partner: Relation to stage of the menstrual cycle. ArcI7ives of Sexual Bel7avior 4:583-597.
|
From page 133... ...
Goy, R.W. 1979 Sexual compatibility in rhesus monkeys: Predicting sexual behavior of oppositely sexed pairs of animals.
|
From page 134... ...
Archives of Sexual Behavior 27:445-465. Helmreich, D.L., and J.L.
|
From page 135... ...
1971 The role of gonadal hormones in the sexual behavior of the rhesus monkey and human: A literature survey. ArcI7ives of Sexual Bel7avior 1:61-88.
|
From page 136... ...
Nieman 1995 Short-term fasting affects luteinizing hormone secretory dynamics but not reproductive function in normal-weight sedentary women. Journal of Clinical Endocrinology Ed Metabolism 65:262-267.
|
From page 137... ...
Slob, and R.W. Goy 1973 Effects of castration and replacement therapy on sexual behavior of adult male rhesus.
|
From page 138... ...
1991 The impact of different doses of estrogen and progestin on mood and sexual behavior in postmenopausal women. Journal of Clinical Endocrinology Ed Metabolism 72:336-343.
|
From page 139... ...
Collins 1986 Chronic gonadotropin-releasing hormone agonist treatment suppresses ovulation and sexual behavior in group-living female rhesus monkeys. Physiological Behavior 36:369-375.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.