Pinel Chapter 11 -- Hormones & Sex

RESEARCH PROBLEMS AND HYPOTHESES

& Operational Defininitions

A. Identifying a Research Problem

A problem is an unanswered question.

The problem selected for study depends in part upon the researcher's

Sources determining research problems:

1. Observation of life events and asking how and/or why they do.

2. Brainstorming happens when two or more people generate ideas for research

3. Theoretical Predictions - regarding what will emerge if a particular explanatory system (paradigm) is valid.

4. Developments in Technology make possible two types of study:

1) studies to investigate old problems in new ways, usually by increases in resolution.

2) advances generate new problems. E.g. Computers leading to studies in artificial intelligence.

a. Computer Data Analysis now permits efficient accumulation, management, and analysis of huge amounts of information not previously possible.

b. Computer Control permits the precise application of stimuli, instructions, and apparatus control. In addition to recording, storing, and analyzing data.

c. Computer Simulations can be utilized to model psychological and other processes.

Knowledge of Research Literature

Science is based upon the research literature. Without it all would have to start from zero. Familiarity with the literature in a discipline can help clarify and select problems and defines what it means to be a professional.

Problems can be generated by:

a. Identifying gaps (laguna) in existing knowledge. We know about “A”, and we know about “C”. What about “B”?.

b. Encountering contradictory findings. E.g. research on extra sensory perception

c. Replication of previously published research result. “Do you believe everything you read?”

Searching the Research Literature

Psychological Abstracts

World Wide Web - the NIH's National Library of Medicine is clearly the best resource for searching topics in the health sciences, including Psychology.

www.nlm.nih.gov - go to PubMed page

B. Hypotheses - A hypothesis is a statement, which if true, solves the problem. It is a tentative explanation which formulates the problem so it can be studied systematically.

1. Research Hypotheses specify a possible relationship between different aspects of the problem, i.e. between the IV and the DV.

2. Research Hypotheses are assessed by two criteria:

a. Does the hypothesis state a relationship between the variables? It should also serve to narrow the problem down to specific variables and/or contexts.

b. Is the hypothesis testable? Careful wording is important, and the terms should be definable (operationally), observable, and measureable.

C. Null Hypotheses - (not to be confused with research hypotheses)

A null hypothesis is a special type of hypothesis associated with statistical analysis.

Traditionally, a null hypothesis states for the problem at hand,

“No relationship exists between the variables”.

It is the common wisdom that is assumed (by experts or the population at large) to be true, and which the experimenter sets out to attack and prove wrong.

It is what would be expected, either by logic or by experience (prejudice?).

E.g. “A fair coin tossed 100 times, will show an equal number of heads and tails.”

Lecture 11a THE NEUROENDOCRINE SYSTEM AND THE EFFECTS OF

GONADAL HORMONES ON EARLY SEXUAL DIFFERENTIATION

1. The Neuroendocrine System

c. Control of the Pituitary by the Hypothalamus

2. Early Sexual Differentiation

c. Internal Reproductive Ducts

d. External Reproductive Organs

e. Brain Development

1. The Neuroendocrine System

- before I describe how hormones influence sexual development, I am going to introduce the fundamentals of neuroendocrine function, with an emphasis on the gonadal hormones

a. Pituitary Gland (use Digital Image CH11F02.BMP)

the pituitary gland is often referred to as the "master gland" because it releases a variety of hormones, called tropic hormones, which travel through the blood to other glands and stimulate them to release hormones which have diverse, long-lasting effects

the pituitary is in fact two glands: the anterior pituitary and the posterior pituitary, which dangle together from the pituitary stalk, which is attached to the hypothalamus

- strictly speaking, it is the anterior pituitary that is the master gland;

only it releases tropic hormones

b. Gonadal Hormones

- within the context of sexual behavior, the gonads (testes and the ovaries) are the

most relevant targets of the anterior pituitary, and gonadotropic hormones are its most

- it is important to realize that both the ovaries and testes release exactly the same

hormones, although they release them in different amounts during various stages of

- the three major categories of gonadal hormones are: estrogens (e.g., estradiol),

androgens (e.g., testosterone), and progestins (e.g., progesterone); the adrenal cortex

releases the same hormones but in smaller amounts

c. Control of the Pituitary by the Hypothalamus

- a major difference between men and women is that gonadotropin release from the

anterior pituitary cycles approximately every 28 days in women, but its release varies

little from day to day in men; the release pattern for both sexes is pulsatile; attempts to

understand this male-female difference led to an important discovery

- first, it was assumed that male and female pituitaries are fundamentally different

(steady vs. cyclic), but female pituitaries implanted in males became "steady pituitaries",

and male pituitaries implanted in females became "cyclic pituitaries"; this suggested that

the pattern of anterior pituitary release was being controlled by another organ; it

suggested that "the master gland had its own master"

- attention naturally turned to the hypothalamus, the neural structure to which the

pituitary is connected; it was soon discovered that the hypothalamus controls the

pituitary in two different ways:

one way for the posterior pituitary and one for the anterior pituitary

(use Digital Image CH11F04.BMP)

- axons of neurons in the paraventricular and supraoptic nuclei of the hypothalamus terminate in the posterior pituitary (use Digital Image CH11F03.BMP)

- vasopressin and oxytocin are synthesized in the cell bodies of these neurons,

they are transported down their axons, and they are released from the posterior

pituitary into general circulation;

vasopressin facilitates reabsorption of water by the kidneys;

oxytocin stimulates contractions of the uterus and ejection of milk in women

(in orgasm, it is released in both females and males but its function in males is unknown)

- the release of tropic hormones from the anterior pituitary is controlled by other

hormones called releasing hormones;

releasing hormones are released by the hypothalamus into the ypothalamopituitary portal system, which carries them to the anterior pituitary;

gonadotropin-releasing hormone stimulates release of the anterior pituitary's two

follicle stimulating hormone and luteinizing hormone

- in general, release of gonadal hormones is influenced by feedback; usually negative, which maintains steady hormone levels;

the hormone surges observed during puberty and in females just prior to ovulation seem to be associated with switches from a negative feedback mode to a positive feedback mode (use Digital Image CH11F05.BMP)

2. Early Sexual Differentiation

a. The "Mamawawa"

- This is the MEN-ARE-MEN-and-WOMEN ARE WOMEN assumption;

the tendency to assume that men and women are distinct opposites with respect to hormones,

that men have male hormones that give them male bodies and brains and make them do male things, and

that women have female hormones that give them female bodies and brains and make them do the opposite, i.e., female things

- you will learn that virtually nothing about this fabled assumption is correct

- the differentiation of male and female gonads occurs about 6 weeks after

at this time males and females have identical primordial gonads, each with

a medulla and a cortex

- in males (XY), the Y sex chromosome triggers the manufacture of a protein called H-Y antigen, which causes the medulla (core) of the primordial gonads to develop into testes

- if no H-Y antigen is present (as in normal genetic females), the cortex of the primordial gonads naturally develops into ovaries

- accordingly, genetic female fetuses injected with H-Y antigen develop testes, and

genetic male fetuses injected with a drug that blocks H-Y antigen develop ovaries

c. Internal Reproductive Ducts

- 6 weeks after fertilization each fetus has two sets of undeveloped internal

reproductive ducts, one male and one female;

the undeveloped male system is called the Wolffian system;

the undeveloped female system is called the Müllerian System

- in normal genetic males, the testes release androgens in the third month and this

causes the Wolffian system to develop;

the testes also release Müllerian-inhibiting substance, which causes the Müllerian system to degenerate and the testes to descend into the scrotum;

all fetuses exposed to androgen in the third month, whether genetic male or female,

develop male ducts

- any fetus, not exposed to androgens in the third month after conception (e.g., a

normal genetic female, an ovariectomized genetic female, or an orchidectomized genetic

male) will develop female reproductive ducts

- ovariectomy refers specifically to removal of the ovaries;

orchidectomy refers specifically to removal of the testes;

castration and gonadectomy refer generally to removal of gonads

d. External Reproductive Organs

- every normal human fetus begins with the precursors of both testes and ovaries and

the precursors of both male and female internal reproductive ducts,

but female and male fetuses have the same bipotential precursor of external

- the surge of androgen release in the third month of fetal development causes

this bipotential precursor to develop into male external genitals;

in the absence of androgen bipotential precursor develops into female external genitals

e. Brain Development

- there is growing evidence of differences between men and women in terms of

overall brain size, the size of specific structures in the brain, and in patterns of brain

- similar to the differentiation of other body organs, sexual differences in the brain

appear to depend on exposure to high levels of androgens at developmentally crucial

- rats are a convenient species for the study of the sexual differentiation of the brain

because when they are born, the period during which the development of their

reproductive organs can be influenced by hormones has passed but the period during

which the development of the brain is maximally influenced by hormones is just

- most research on brain differentiation has focused on the differentiation of the

hypothalamus-controlled pattern of gonadotropin release into the steady male pattern or

the female cyclic pattern

- consistent with what you have already learned about reproductive-system

rats exposed to androgens in the perinatal period (e.g., intact genetic male

rats; intact genetic female rats injected with androgen; ovariectomized female rats

injected with androgen) develop the steady, male pattern of gonadotropin release

- in contrast, rats not exposed to androgen in the perinatal period (e.g., intact genetic

female rats; ovariectomized genetic female rats; orchidectomized genetic male rats)

develop the cyclic, female pattern of gonadotropin release

- evidence supports the idea that in order to masculinize the rat brain

testosterone must be converted to estradiol--a process called aromatization

- the aromatization hypothesis is that testosterone released during the perinatal

period enters the brain and is aromatized to estradiol and that it is actually estradiol

that masculinizes the brain

[WHAT??? Are you AWAKE? Estradiol is a female hormone.]

- Sorry, there are four lines of evidence that support this theory:

(1) the enzyme necessary for aromatization is present in the neonatal rat,

(2) neonatal injections of estradiol masculinize the rat brain,

(3) dihydrotestosterone, a nonaromatizable androgen, does not masculinize the rat brain, and

(4) agents that block aromatization block the masculinizing effects of neonatal testosterone injections

- several documented differences between men and women have been seen in the

brains of humans;

men's brains are about 15% larger, have a higher metabolic rate in the temporal

lobe and limbic system;

women have a more extensive corpus callosum and have higher metabolic activity in the cingulate gyrus;

other differences are found in the anatomy of the hypothalamus, thalamus and anterior commisure

- research is currently focusing on the functional significance of these differences

- with respect to early development the "mamawawa" hypothesis is clearly incorrect;

Everybody is born with a female program of development;

in normal males, the development of ovaries is overridden by H-Y antigen, and testes develop;

then the androgens released by the testes override the program for the development of female reproductive organs and brains, and the male equivalents develop

- hormone injections or gonadectomy at the appropriate stage of development can

produce individuals whose bodily sex is different from their genetic sex;

maleness and femaleness are but variations of the same, fundamentally female

program of development

Suggested Websites for Lecture 11a:

Gender and Brain: http://www.science.ca/scientists/Kimura/kimura.html

A biography of sorts of Doreen Kimura, highlighting her work on sex differences in brain function.

Sexual Disorders Related to Pituitary Dysfunction: http://medstat.med.utah.edu/kw/human_reprod/

The homepage of the Pituitary Tumors Network Association; see their links to hormonal imbalances and to sexual and reproductive dysfunction.

Behavioral Neuroendocrinology: http://www.sbne.org/

Homepage for the Behavioral Neuroendocrinology Society and its journal, Hormones and Behavior.

Lecture 11b -- THE EFFECTS OF SEX HORMONES IN PUBERTY AND ADULTHOOD

1. The Role of Hormones in Pubertal Development

2. Effects of Hormones in Adulthood

c. Anabolic Steroids

3. Androgenic Insensitivity Syndrome

4. The Hypothalamus and Sexual Behavior

5. Sexual Preference

1. The Role of Hormones in Pubertal Development

- At the beginning of puberty, there is a surge in the release of growth hormone and of both the gonadotropic hormones from the anterior pituitary

- in males the surge in gonadotropic hormones increases the release of androgens from the testes

- this masculinizes the body and putitatively the brain; there is muscle development, body hair and pubic hair growth, lowering of the voice, the development of fertility, growth of sex organs, brain changes, etc.

- in females the pubertal surge of gonadotropin release stimulates the release of estrogens from the ovaries

- this partially feminizes the body; estrogens stimulate breast growth, hip growth, onset of the menstrual cycle, fertility, etc.

- the growth of pubic hair and axillary hair (underarm hair) is stimulated by androstenedione, an androgen released by the adrenal cortex, thus the "mamawawa" stumbles again

2. Effects of Hormones in Adulthood

- hormones not only influence the development of the body and brain along male or

female lines, they play a role in activating the sexual behavior of men and women

- the role of androgens in activating the sexual behavior of adult males is apparent following orchidectomy

- in about half the cases, there is a complete loss of ability to achieve an erection and of sexual motivation within a week or two of the operation; however, in other cases, the decline is less complete and/or more gradual; the reason for this variability is not understood

- castrated men also exhibit a variety of physical changes, e.g., reduction of body hair, deposition of fat on hips and chest, softening of the skin, a marked reduction of strength

- testosterone replacement injections restore sexual motivation, sexual potency, and remasculinize the bodies of orchidectomized males; but they remain sterile

- the fact that testosterone injections restore the sexuality of orchidectomized males has led to the view that the sexual motivation and performance of a male is determined by his level of testosterone, and thus that these can be increased in healthy intact males by testosterone injections