Lecture 10: Pathophysiology of the hypothalamic-pituitary-ovarian axis

Question 1

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Answer 1

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Question 2

What are some other factors that can influence the HPO axis:

Answer 2

Dopamine (-ve feedback on AP to inhibit prl)
Central drive (Stress, low BW, intercurrent illness)
Prolactin (Pituitary adenoma or hyperplasia)
Androgens (Tumors ovary or adrenal, cushings syndrome)
Premature ovarian insufficiency
Insulin resistance ( high androgens +/- obesity [PCOS])
TSH (hyper or hypo)

Question 3

What does high prolactin do?

Answer 3

Breastmilk

Question 4

What lab tests can you do for oligiomenhorrea:

Answer 4

• bHCG
• LH level
• FSH level
• Estradiol
• Progesterone
• Free testosterone
• Prolactin
• TSH

Question 5

Write some notes on prolactin secretion:

Answer 5

• Prolactin secretion by lactotrophs in the anterior pituitary is normally suppressed by the neurochemical dopamine
• Drugs that block dopamine or deplete dopamine result in prolactin
• Prolactin negatively feeds back to hypothalamus and affects pulsatile secretion of GnRH (which affects ovulation)

Question 6

What can result in high prolactin level:

Answer 6

Anterior pituitary tumour

• Macro or microadenoma
• Prolactinoma

Drugs
- Psychotropic drugs (interfere with dopamine metabolism) i.e haloperidol, stelazine

Lactation
Stress

Question 7

How can the pituitary gland be imaged?

Answer 7

• Xray
• CT
• MRI

Question 8

Describe treatment of prolactinoma:

Answer 8

Bromocriptine or cabergoline

• Dopamine agonist
• Reduces tumor size in 80% (side effect nausea)

Surgery

Question 9

What is the possible diagnosis for an athletic female, 16 y/o breast and pubic development without menses:

Answer 9

Think hormone or anatomical

• Primary amenorrhea
• First exclude pregnancy
• Hypothalamus; Stress,exercise, anorexia, low body fat index
• Anterior pituitary; Prolactinoma, thyroid, dopamine
• Ovary; PCOS, Premature ovarian insufficiency
• Uterus; Absent uterus, atrophic endoemtrium
• Vagina; Imperforate hymen, vaginal septum

Question 10

How does stress relate to the HPO acis?

Answer 10

Stress can result in decreased central drive (Stress, low body weight, intercurrent illness)

Question 11

What investigations can you do for the athletic female, 16 y/o breast and pubic development without menses:

Answer 11

• bHCG (exclude pregnancy)
• LH,FSH
• Estradiol, progesterone
• Free testosterone
• TSH
• Prolactin

Imaging: MRI

Question 12

How do you manage primary amenorrhea:

Answer 12

Counselling
- Expectant, weight/fat gain
Hormone therapy
- COCP
Regular follow up
Review when considering starting a family

Question 13

Go over all the cases in this lecture

Answer 13

now

Question 14

What lab tests can you do for a pt with secondary infertility

Answer 14

Lab tests:

• Day 3 FSH, estradiol
• Day 21 progesterone
• AMH
• Semenanylsis
• TSH

Imaging

• Pelvic ultrasound
• Hysterosalpingogram

Question 15

How do you manage premature ovarian insufficiency:

Answer 15

• Counseling and psychological support
• Refer fertility specialist
• Prognosis: sporadic ovulation vs donor egg
• If not wishing pregnancy, offer menopausal hormone therapy