Lecture 70: Reproductive Endocrinology

Question 1

The _____________ is the neural control center for repro hormones.

Answer 1

Hypothalamus

Question 2

Describe the simple neural reflex of regulation of reproduction

Answer 2

Employs the nerves that release simple neurotransmitters directly into target tissue

Question 3

Describe the Neuroendocrine Reflex regulation of reproduction

Answer 3

Requires a neurohormone (released by a neuron) to enter the blood and act on remote target tissue

Question 4

The pituitary gland is positioned in the depression of the sphenoid bone, called the _______ _______.

Answer 4

Stella turcica

Question 5

The third ventricle separates the ________ portions of the hypothalamus.

Answer 5

Lateral

Question 6

What is the Hypothalamo-Hypophyseal Portal System (HHP)?

Answer 6

The HHP system allows minute (picograms) quantities of releasing hormones to act on the anterior pituitary before they are diluted by the general circulation

Question 7

What is the relationship between the portal vascular system (PVN) and the posterior pituitary?

Answer 7

Axons from neurons originating in the hypothalamus (PVN) extend into the posterior pituitary where they release their neurohormones into a capillary plexus

Question 8

True or False: The posterior pituitary has a portal system.

Answer 8

FALSE
Neurohormones are deposited directly into systemic circulation

Question 9

Which repro hormones are classified as hypothalamic hormones?

Answer 9

Gonadotropin Releasing Hormones (GnRH)

Question 10

Which repro hormones are classified as Pituitary Hormones?

Answer 10

Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Prolactin
Oxytocin

Question 11

Which repro hormones are classified as gonadal hormones?

Answer 11

Estradiol (E2)
Progesterone (P4)
Prostaglandin F2-alpha
Equine Chorionic Gonadotropin (ECG)
Human Chorionic Gonadotropin (HCG)

Question 12

Which repro hormones are classified as neurohormones and what is their mode of action

Answer 12

GnRH, FSH, LH, Oxytocin

Synthesized by neurone and are released directly into the blood to cause a response in a target tissue somewhere else in the body

Question 13

Which repro hormones are classified as releasing hormones and what is their mode of action

Answer 13

GnRH

• Synthesized by neurons in the hypothalamus and causes release of other hormones from the anterior pituitary
• They can also be classified as neurohormones because they are synthesized and released by neurons

Question 15

Which repro hormones are classified as sexual promoters and what is their mode of action

Answer 15

Estrogen, Progesterone, Testosterone, cEG, hCG
- Secreted by the gonads to stimulate the repro tract, regulate the function of the hypothalamus and anterior pituitary, and regulate reproductive behavior

Question 16

Which repro hormones are classified as pregnancy maintenance hormones and what is their mode of action

Answer 16

Progestins and Placental Lactogen

High concentration during pregnancy
Responsible for maintaining pregnancy and assisting the female in lactation ability

Question 16

Which repro hormones are classified as luteolytic hormones and what is their mode of action

Answer 16

PGF2-alpha

Causes destruction of the corpus luteum

Question 16

Which repro hormones are classified as general metabolic hormones and what is their mode of action

Answer 16

Thyroxin, Adrenal corticoids, and growth hormone

Promote metabolic well-being

Question 17

State which repro hormones are biochemically classified as peptides, glycoproteins, steroids, and prostaglandins

Answer 17

Peptides: GnRH is a decapeptide, Prolactin and Relaxin
Glycoproteins: FSH, LH, Inhibin
Steroids: Progesterone, estradiol, testosterone
Prostaglandins: PGF2-alpha and PGE2

Question 18

Protein hormones bind to what type of receptors?

Answer 18

Plasma bound receptors

Question 19

Steroid hormones bind to what type of receptors?

Answer 19

Travel freely through plasma membrane into the cytoplasm and bind directly to specific nuclear receptors

Question 20

Describe the difference in a fast response vs slow response from a steroid hormone. Give examples of each

Answer 20

Fast response: binds to a membrane receptor causing protein production
example: Estradiol increases myometrial contractions and progesterone decreases myometrial contractions

Slow response: Binds to nuclear receptor inside cell causing protein production
example: estradiol causes mucous secretion by the female tract and progesterone causes uterine gland secretion

Question 21

How does the CNS regulate the reproductive system?

Answer 21

Receives, processes and interprets sensory inputs (such as olfactory, visual, feedback systems, and photoperiod

These inputs ultimately regulates GnRH release

Question 22

What is the main role of the hypothalamo-pituitary gonadal axis?

Answer 22

Regulates reproduction based upon a positive and negative feedback system

Hormones can have both positive and negative feedback on different areas

Question 23

Steroid hormones are metabolized where? What about protein hormones?

Answer 23

Steroid hormones are metabolized by the liver
Protein hormones are degraded in the liver and kidneys

Question 24

Which of the following does the pituitary secrete?
A) Oxytocin, FSH, LH
B) Testosterone and Inhibin
C) FSH and Progesterone
D) Estrogen and Inhibin

Answer 24

Oxytocin, FSH and LH

Question 25

Do males have a surge center?

Answer 25

NO!

The surge center in females is essential for ovulation, males obviously don’t need this

Question 26

What is the mechanism of “Defeminization” in the male?

Answer 26

Testosterone produced by the testes of the developing male fetus penetrates the blood-brain barrier.

Once the testosterone is in the brain, it is converted to Estradiol

Actually is estradiol that defeminizes the hypothalamus and causes the surge center to not develop

Question 27

How does estradiol not cause defeminization in the female brain?

Answer 27

In the female, estradiol is bound to alpha-fetoprotein which prevents the estradiol from crossing the blood brain barrier

Question 28

What is puberty?

Answer 28

The process of acquiring reproductive competence

Question 29

The onset of puberty is dependent upon what?

Answer 29

Dependent upon the ability of the hypothalamic neurons to produce GnRH in sufficient quantities to support gametogenesis

Question 30

In the male, the onset of puberty is brought about because of decreased hypothalamic sensitivity to what?

Answer 30

Decreased hypothalamic sensitivity to negative feedback by Testosterone and Estradiol

Question 31

What is a factor that causes accelerated puberty in sows?

Answer 31

Boar exposure (pheromones)