Reproductive and urinary systems

Gonads

Sex organs that contain germ cells and produce gametes and sex hormones

Testosterone

• principle male sex hormone

• Potent androgen

• Synthesized within the leydig cells of the testes

• Some synthesized in the adrenal cortex - in both f and m

What is testosterone responsible for ?

• development and maintenance of the male secondary sexual characteristics

• Primary hormone from which other sex hormones can be produced

DHEA

• dehydroepiandrosterone - weaker version of testosterone

• Responsible for the early development of pubic / body hair in boys and girls

Describe the anatomy from which testosterone is produced

• highly folded seminiferous tubules excrete testosterone from leydig cells

• Sertoli cells produce other hormone regulating hormones

What hormones is testosterone a precursor for ?

• in men - dihydrotestosterone (active metabolite)

• In women - estrodiol (active metabolite)

• Androsterone ( inactive)

• Etiocholanolone (inactive)

Synthesis pathway for steroid hormones

Actions of Testosterone

• stimulates enlargement of tastes and male accessory organs

• Stimulates development of male secondary sex characteristics

Male secondary sex characteristics

1. Increased growth of body hair

2. Enlargement of the larynx and thickening of vocal chords

3. Thickening of the skin

4. Muscle growth, widening of shoulders, narrowing of waist

5. Thickening and strengthening of bones

Action of DHT

• binds to cytoplasmic androgen receptors

• Binding promotes release of heat shock protein (hsp)

• Steroid receptor complex migrates to nucleus

• Binds to specific regions of DNA that contain Androgen response elements (ARE)

• Drives expression of genes that determine male phenotype

Why Androgen receptors and AREs important to women too ?

• help with the development of pubic and axillary hair

How do Testosterone levels of men and women change throughout their lives ?

• mini puberty at 6 months

• Hormone levels unchanged until puberty

• Increased during puberty

• Maintain throughout adult life - decline in old age

What organs does testosterone target ?

• Brain

• Skin

• Kidney

• Male sex hormones

• Bone

• Bone Marrow

• Fat

• Liver

• Muscle

How does Testosterone affect the brain, skin and kidney

1. Brain - libido, aggression, cognition

2. Skin- Male pattern body, facial hair, balding and increased sebum production

3. Kidney- stimulation of erythropoietin production

How does Testosterone affect the Male sexual organs, bone and bone marrow ?

1. Male sexual organs - penile growth, spermatogenesis, prostate growth and function

2. Bone - accelerated linear growth, closure of epiphyses, maintains BMD

3. Bone Marrow - Stimulation of stem cells

How does Testosterone affect fat, liver and muscle ?

1. fat - decrease in mass

2. Liver - synthesis of serum proteins

3. Muscle - increase in strength and volume

Which organs secrete hormones in males ?

• hypothalamus

• Anterior pituitary gland

• Testes

Which hormones does the brain use to control reproduction in both sexes ?

1. GnRH - gonadotropin releasing hormone - acts on the hypothalamus - triggers short-loop negative feedback

2. Triggers lutenizing hormone (LH) and Follicle Stimulating hormone (FSH) - which act on the gonads

Describe the feedback effects of sex steroids on gonadotropin release

What do the ovaries produce ?

Female sex hormones and female germ cells

Describe the evolution of the ovum throughout the menstrual cycle

1. Primary follicle

2. Theca

3. Antrum

4. Ovulation

5. Corpus luteum formation

6. Mature corpus leteum

7. Corpus albicans

Describe the cellular structure of the antrum (Tertiary follicle)

Describe the 3 categories of Ovarian Steroid Hormones ?

1. Estrogens C18 (produced by Granulosa cells)

2. Progestagens C21 ( produced by Corpus Luteum Cells)

3. Androgens C19 ( produced by Theca cells)

Estrogens C18

1. 17 B-Estradiol (E2) - most potent type of estrogen - regulates menstrual cycle - present from puberty to menopause

2. Estrone (E1) - post menopause - weaker type of estrogen - synthesized from fat

3. Estriol - E3 - present in pregnancy

Progestagens C21

1. Pregnenolone

2. Progesterone

3. 17 OH Progesterone

Androgens C19

• DHEA

• Androstenedione

• Testosterone

• Dihydrotestosterone

How are the actions of estrogen mediated ?

• Estrogen Receptor (ER) is a dimeric nuclear protein that binds to DNA and controls gene expression

• Estrogen:ER complex binds to specific DNA sequences called hormone response element to activate the transcription of target genes

Main actions of Estrogen

1. Development and regulation of the female reproductive system and secondary sex characteristics

2. Provision of the hormonal timing for ovulation

How does estrogen affect the brain, breasts and skin of the female body ?

1. Brain - helps adjust body temp, increase memory, adjusts libido

2. Breast - grows and shapes breast, preparation for breast feeding

3. Skin - makes skin young

How does estrogen affect the Bone, Vagina nd Uterus of the female body ?

1. Bone - strengthens bone and increases its density

2. Vagina - moistens, protects from infection

3. Uterus - monthly preparation for pregnancy or menstrual cycle