Biology: Leydig Cells and Androgens lec 4

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Questions and Answers

What type of steroids do Leydig cells secrete?

C18 steroids

C25 steroids

C21 steroids

C19 steroids (correct)

What is the function of Müllerian inhibiting hormone secreted by Sertoli cells?

Enhances development of female accessory sex organs

Inhibits development of female accessory sex organs (correct)

Enhances development of male accessory sex organs

Inhibits development of male accessory sex organs

What is the function of inhibin secreted by Sertoli cells?

Stimulates LH release from the anterior pituitary

Stimulates FSH release from the anterior pituitary

Inhibits FSH release from the anterior pituitary (correct)

Inhibits LH release from the anterior pituitary

What is the location of Leydig cells?

Outside seminiferous tubules Signup and view all the answers

What is the function of androgens in the body?

Involved in all of the above Signup and view all the answers

What is the function of GnRH in the Hypothalamic-Pituitary-Testicular Axis?

Stimulates the release of gonadotropins from the anterior pituitary Signup and view all the answers

What is the function of DHT?

Strong androgen that cannot be aromatized to estrogen Signup and view all the answers

What controls the secretion of Leydig cells?

LH from the anterior pituitary Signup and view all the answers

What is the primary function of Luteinizing Hormone (LH) in the testes?

Stimulates synthesis and secretion of androgens Signup and view all the answers

Which of the following is NOT a function of androgens?

Maintain genital tract Signup and view all the answers

What is the primary function of inhibin?

Feeds back to the pituitary to decrease FSH secretion Signup and view all the answers

Which of the following estrogens is involved in maternal behavior?

Estradiol (E2) Signup and view all the answers

What is the precursor to estrogens?

Androgens Signup and view all the answers

Which of the following is a function of estrogens?

Regulation of calcium metabolism Signup and view all the answers

What is the primary function of progesterone?

Maintenance of pregnancy in mammals Signup and view all the answers

Which of the following hormones is involved in the development of secondary sex characteristics?

Androgens Signup and view all the answers

What is the main function of inhibin?

Inhibits FSH release from anterior pituitary Signup and view all the answers

What type of hormones are produced by the placenta?

Both protein and steroid hormones Signup and view all the answers

What is the function of chorionic gonadotropin (CG/hCG) produced by the placenta?

Acts as a supplementary trophic hormone with LH-like functions Signup and view all the answers

During which phase of life is the Hypothalamic-Pituitary-Gonadal Axis dormant?

Childhood Signup and view all the answers

What is the role of INSL3 in the reproductive system?

Might play a role in the development of reproductive organs Signup and view all the answers

What type of steroids are progestogens?

C21 steroids Signup and view all the answers

During which phase of life does the Hypothalamic-Pituitary-Gonadal Axis become active again?

Puberty Signup and view all the answers

What happens to the Hypothalamic-Pituitary-Gonadal Axis during old age?

It declines Signup and view all the answers

What is the primary effect of oxytocin on uterine contractions?

Increases uterine contractions Signup and view all the answers

What is the primary function of the pineal gland in mammals?

To produce indoleamines, such as serotonin and melatonin Signup and view all the answers

What is the primary function of serotonin in the pineal gland?

To be produced in light Signup and view all the answers

Which hormone is involved in the regulation of epinephrine biosynthesis in the adrenal medulla?

Cortisol Signup and view all the answers

What is the typical duration of a circadian rhythm in hormone secretion?

Approximately 24 hours Signup and view all the answers

What is the primary function of melatonin in the pineal gland?

To regulate the sleep-wake cycle Signup and view all the answers

Which type of hormonal secretion is characterized by the release of hormones in bursts or pulses?

Pulsatile secretion Signup and view all the answers

What type of input regulates hormone secretion in the endocrine system?

Neural and hormonal input Signup and view all the answers

What is the term for the changes in hormone secretion that occur across the year?

Circannual rhythms Signup and view all the answers

What is the primary function of negative feedback in the endocrine system?

To decrease hormone production Signup and view all the answers

What is the term for the changes in hormone secretion that occur across the lifespan?

Changes across the lifespan Signup and view all the answers

What is the primary function of positive feedback in the endocrine system?

To increase hormone production Signup and view all the answers

What is an example of physiological end-products regulating hormone secretion?

Insulin regulating blood glucose levels Signup and view all the answers

Which of the following hormones is NOT regulated by a biological rhythm?

Insulin Signup and view all the answers

What is the function of the pineal gland in non-mammalian vertebrates?

To be photoreceptive Signup and view all the answers

What is the primary mechanism by which oxytocin stimulates uterine contractions?

Increasing oxytocin secretion Signup and view all the answers

Study Notes

Leydig Cells

Located outside seminiferous tubules
Controlled by LH from anterior pituitary
Secrete androgens (C19 steroids)

Androgens

Functions:
- Spermatogenesis
- Genital tract maintenance
- Accessory sex organs
- 2nd-degree sex characteristics
- Metabolism
- Cognition
- Sexual behavior, aggression
- Mood
Types:
- Testosterone
  - Acts as a prohormone for DHT and estrogen
- Dihydrotestosterone (DHT)
  - Strong androgen
  - Can’t be aromatized to estrogen
- Androstenedione
  - Weak androgen

Sertoli Cells

Located inside seminiferous tubules
Controlled by FSH and testosterone
Secrete:
- Müllerian inhibiting hormone (protein)
  - Inhibits development of female accessory sex organs early in development
- Inhibin (protein)
  - Inhibits FSH release from anterior pituitary

Hypothalamic-Pituitary-Testicular Axis

Hypothalamic hormone: GnRH
- Binds to receptors on anterior pituitary
- Stimulates anterior pituitary to synthesize and secrete gonadotropins (LH and FSH)
Anterior pituitary hormone: LH
- Binds to receptors on Leydig cells
- Stimulates growth of Leydig cells
- Stimulates synthesis and secretion of androgens
Anterior pituitary hormone: FSH
- Binds to receptors on Sertoli cells
- Stimulates growth and activity of Sertoli cells
- Stimulates synthesis and secretion of inhibin
Testicular hormones: Androgens
- Feed back to hypothalamus and pituitary to regulate GnRH, LH, and FSH secretion
- Influence development, structure, and activity of body and brain

Estrogens

Synthesized from androgens
Functions:
- Genital tract maintenance
- 2nd-degree sex characteristics
- Water retention
- Ca++ metabolism
- Cognition
- Sexual behavior
- Maternal behavior
Types:
- 17β-Estradiol (E2)
- Estrone (E1)
- Estriol (E3)

Progesterone

Function: Pregnancy maintenance in mammals
Also involved in sexual behavior and maternal behavior

Inhibin

Function: Inhibits FSH release from anterior pituitary

Placenta

Temporary organ
Protein hormones:
- Chorionic gonadotropin (CG/hCG)
- Placental lactogen (PL)
- Chorionic corticotropin (CC)
- Chorionic thyrotropin (CT)
Steroid hormones:
- Estrogens
- Progestogens
- Corticosteroids
- Androgens

Hypothalamic-Pituitary-Gonadal Axis Across the Lifespan

Active during prenatal period and infancy
Dormant during childhood (prepubertal hiatus)
Becomes active during puberty (reawakening)
Active during adulthood
Declines during old age (reproductive senescence)

Pineal Gland

Photoreceptive in non-mammalian vertebrates
Endocrine gland in mammals
Produces indoleamines (derivatives of tryptophan):
- Serotonin
- Melatonin
Melatonin:
- Produced in dark
- Circadian rhythms
- Sleep/wake cycle
- Reproductive effects (seasonal breeding)

Regulation of Endocrine Function

Regulation of hormone secretion by:
- Neural input
- Hormones
- Physiological end-products
- Negative feedback
- Positive feedback
- Regulation of hormone biosynthesis
- Biological rhythms (circadian, pulsatile, circannual, and changes across the lifespan)

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Description

This quiz covers the functions and characteristics of Leydig cells, including their location, control, and secretion of androgens. It also touches on the chemical structure of androgens and their precursors.