[PHARM] Male Hormones part 1

Testis Functions

Onset controlled largely by FSH secretion by the adenohypophysis of the pituitary

• Gametogenic

• Endocrine

Testis Functions

High concentrations of testosterone are locally required for continuing sperm production (in seminiferous tubules)

• Gametogenic

• Endocrine

Testis

• Have FSH receptor

• May be the source of estradiol produced in the testes via aromatization of locally produced testosterone

• Synthesize and secrete a variety of active proteins including:

→ Müllerian duct inhibitory factor

→ Inhibin and Activin

• SERTOLI CELLS

• INTERSTITIAL CELLS OF LEYDIG

Testis

• Found in the spaces between seminiferous tubules

• Produced testosterone with LH stimulation

• SERTOLI CELLS

• INTERSTITIAL CELLS OF LEYDIG

Androgen

• Most important androgen secreted by the testis

• In men, 8 mg of testosterone is produced daily

→ 95% - produced by Leydig cells

→ 5% - produced by adrenals

• Testosterone

• Estrogen

• Progesterone

Androgen

• 65 % of circulating testosterone is bound to sex hormone binding globulin (SHBG)

• SHBG is __________ in plasma by:

→ Estrogen

→ Thyroid hormone

→ Cirrhosis of liver

• increased

• decreased

Androgen

• 65 % of circulating testosterone is bound to sex hormone binding globulin (SHBG)

• SHBG is __________ in plasma by:

→ Androgen

→ Growth hormone

→ Lower in Obese person

• increased

• decreased

Androgen

• Organ for the major pathway for the degradation of testosterone

→ reduction of the double bond and ketone in the A ring, as is seen in other steroids with a Δ 4 -ketone configuration in the A ring

→ leads to the production of inactive substances such as androsterone and etiocholanolone that are then conjugated and excreted in the urine

• Kidney

• Bladder

• Liver

Androgen

• Adrenal Androgens

• Contribute slightly to the normal maturation process supporting other androgen-dependent pubertal changes in the human, primarily development of pubic and axillary hair and bone maturation

• Can be converted by peripheral tissues to estrone in very small amounts (1–5%). The P450 aromatase enzyme responsible for this conversion is also found in the brain and is thought to play an important role in development.

• Androstenedione

• Dehydroepiandrosterone (DHEA)

• Dehydroepiandrosterone Sulfate (DHEAS)

Physiologic Effects

• Responsible for penile and scrotal growth

• Appearance of pubic, axillary, beard hair

• Sebaceous glands become more active

• Skin becomes thicker and oilier

• Larynx grows, vocal cords become thicker (low-pitched voice)

• Skeletal growth is stimulated, epiphyseal closure is accelerated

• Growth of prostate and seminal vesicles

• Darkening of skin, increase skin circulation

• Testosterone

• Androgens

• DHEA and DHEAS

• Androstenedione