Pregnancy - Endocrine Changes

Question 1

Pregnancy and Progesterone

Answer 1

Progesterone
during the first 2 weeks stimulates the fallopian tubes to secrete the nutrients the zygote/blastocyst requires
placenta starts production at 6 weeks and takes over at 12 weeks
progesterone inhibits uterine contractions by
1. Inhibiting production of prostaglandins
2. Decreasing sensitivity to oxytocin
stimulates development of lobules and alveoli

Question 2

Pregnancy and Oestrogen

Answer 2

Oestrogen
oestriol is major oestrogen (not oestradiol)
stimulates the continued growth of the myometrium
stimulates the growth of the ductal system of the breasts

Question 3

Pregnancy and Prolactin

Answer 3

Prolactin
increase during pregnancy probably due to oestrogen rise
initiates and maintains milk secretion of the mammary gland
essential for the expression of the mammotropic effects of oestrogen and progesterone
oestrogen and progesterone directly antagonises the stimulating effects of prolactin on milk synthesis

Question 4

Pregnancy and hCG

Answer 4

hCG
secreted by syncitiotrophoblast, stimulated by GnRH produced in adjacent cytotrophoblast
can be detected within 9 days, peak secretion at 9 weeks
mimics LH, thus rescuing the corpus luteum from degenerating and ensuring early oestrogen and progesterone secretion
stimulates production of relaxin
may inhibit contractions induced by oxytocin

Question 5

Pregnancy and Other Hormones

Answer 5

Also
Relaxin: suppresses myometrial contractions and relaxes the pelvic ligaments and pubic symphysis
hPL: has lactogenic actions (insignificant with respect to prolactin) - antagonises insulin, therefore making less glucose available to the mother - enhances protein metabolism

Question 6

Pregnancy Hormones - Example Question

Answer 6

A 42-year-old woman was seen in Endocrinology Clinic with a 4 month history of amenorrhoea. On questioning she reports having to wax her arms and upper lip. Her mother went through early menopause at 28 after having an emergency hysterectomy post-partum. On examination her BMI is 38 but otherwise unremarkable.

Her GP has kindly ordered blood tests prior to her appointment

Investigations

LH	40 IU/L (5 to 25 IU/L)
FSH	8 IU/ (1 to 11 IU/L)
Estradiol	720 pmol/L (70-500 pmol/L)
Progesterone	220 nmol/L (35-92 nmol/L)
Thyroid Stimulating Hormone	5.6 mIU/L (0.5 -6.0 mIU/L)
Prolactin	700 mIU/L (105-548mIU/L)

What is the most likely diagnosis?

	Prolactinoma
	Polycystic Ovarian Syndrome
	Premature Ovarian Failure
	> Pregnancy
	Subclinical Hypothyroidism

The most likely diagnosis is pregnancy. The elevated estrodiol and progesterone is characteristic with a slight rise in the LH level.

The prolactin level is only mildly elevated so a prolactinoma is unlikely especially with the rise is other hormone levels. Polycystic ovarian ayndrome is associated with androgen excess and an elevated LH to FSH ratio. While androgen (testosterone) hasnt been measured, it is not associated with rises in estradiol or progesterone.

Premature Ovarian Failure typically presents with low levels of estradiol and a raised FSH level. Subclinical Hypothyroidism is linked with oligoovulation but in this case the TSH level is normal excluding this as a diagnosis

Question 7

Interpreting FSH, LH, Progesterone

Answer 7

Pregnancy:

• Elevated Estradiol + Progesterone
• Slight rise in LH
• Slight rise in Prolactin

Prolactinoma:
- Markedly raised Prolactin

PCOS:

• Androgen excess i.e. High testosterone
• Elevated LH:FSH ratio
• No increase in estradiol or progesterone

Premature Ovarian Failure

• Low levels estradiol or progesterone
• Raised FSH