Lecture 10: Disorders of the HPO axis

Question 1

Where is prolactin made, what inhibits it and what does it inhibit

Answer 1

Prolactin is made by lactotrophs in the anterior pituitary.

Dopamine normally inhibits prolactin secretion by having negative feedback on the Anterior pituitary

Prolactin has a negative feedback on the Hypothalamus which affects the pulsatile secretion of GnRH

Question 2

What are different causes of some one having high Prolactin and low-normal FSH, LH (everything else)

and what are the presentations

• not pregnant

Answer 2

Presentation

• milk expressed on breast exam
• irregular/ light menstrual cycles: anovulation/oligo-ovulation
• if ant pit tumour: headaches, visual disturbance, balance problems

Causes
- Psychotropic drugs that interfere with dopamine metabolism- eg. Haloperidol

• Anterior Pituitary tumour: macro or microadenoma, prolactinoma
• Lactation- still breast feeding
• Stress

Question 3

How is prolactinoma treated

Answer 3

1. Bromocriptine or Cabergoline which is a dopamine agonist,
   - reduces size of the tumour, returning prolactin levels to normal in 80% of patients but needs to be introduced slowly due to SE nausea
2. Surgery: transphenoidal resection via sella tursica

Question 4

What is the presentation of 1’ Ammenorrhea including expected HPO hormone profile

Answer 4

Although secondary sex characteristics have developed, there is no menses in a teenage girl

Low LH and FSH, E2 and P2. But prolactin and TSH levels normal

Question 5

What is the first test to do when there is ammenorrhea

Answer 5

pregnancy test

Question 6

What are different causes for 1’ amenorrhea at different places of the HPO axis

Answer 6

Congenital:
- imperforate hymen, vaginal septum, absent uterus, atrophic endometrium

Ovary problems: PCOS, premature ovarian insufficiency

Other hormones in the Ant. Pituitary reducing LH and FSH release- eg prolactinoma

Hypothalamus release of GnRH decreased due to decreased central drive
-Stress, exercise, anorexia nervosa, low BMI, intercurrent illness

Question 7

How is 1’ amenorrhea managed in teen girl

Answer 7

• Counselling for stress reduction
• Weight/fat gain
• COCP hormone therapy for E2 to prevent osteoporosis

All requires regular follow up and must be reviewed when starting family

Question 8

What is premature ovarian insufficiency and how does it link to the HPO axis (mechanism)

Answer 8

Ovarian insufficiency leading to amenorrhea in women before the age of 40; most cases are permanent some can be transient

Not many follicles left so ovaries not producing as much E2 which feeds back to Ant Pit and Hypothalamus to secrete more GnRH, FSH and LH

Question 9

How does POI present is it 2nd or 1’ infertility

Answer 9

• Less frequent menses: will likely stop soon
• No vasomotor symptoms yet but will develop symptoms of menopause
• Have to exclude other reasons - make sure on US, hysterosalpinogram patent fallopian tubes,, smears up to date, no STI, pelvic pain etc

Can be 1 or 2ndary: 2ndary if after a previous birth.

Question 10

How is POI managed

Answer 10

• Counselling and psychological support
• Refer to fertility specialist where they can harvest the sporadic ovulation or donor egg

-If not wishing fertility offer menopausal hormone therapy: full combined pill or HT bc still under 50 so will replace to normal levels of hormone