Gynaecological Endocrinology

Amenorrhoea : Prolactin : Biochemical changes in pregnancy : Hirsuties

Day 21 progesterone (nmol/L) for evaluation of the function of the corpus luteum:

Day 21 progesterone is a misnomer as it is only correct for women with 28 day cycles. In order to assess optimal luteal function, progesterone measurements should ideally be made 7 days prior to the next menstrual bleed.

<35

poor luteal function: ovulation unlikely

35-70

optimal luteal function indicating ovulation likely

>70

may indicate suboptimal luteal function unless there is multiple ovulation due to either spontaneous occurrence or due to induction by clomiphene

Amenorrhoea

  LH & FSH Oestradiol
Primary ovarian failure both high but usually FSH > LH low
Weight loss associated amenorrhoea FSH > LH low
Polycystic ovary syndrome LH: FSH ratio is > 2.5:1 in many cases but is an unreliable test for the diagnosis of PCO variable
Pregnancy low LH and FSH  
Oestrogen-secreting tumour low high
Prolactinoma (see below)    

Prolactin

Mildly elevated values ie 600-900 U/L may be due to the stress of venepuncture; samples with values in this range should be checked on a repeat sample.

Elevated levels of prolactin may be due to pregnancy, hypothyroidism and drugs eg phenothiazines, haloperidol, tricyclic anti-depressants, metoclopramide, methyl DOPA & high dose oral contraceptives.

Elevated prolactin levels in the absence of the above conditions requires further investigation for prolactinoma eg full pituitary function tests and imaging.

Biochemical changes during pregnancy

Real changes
  • elevation in hCG
  • increase in alkaline phosphatase due to placental production of the isoenzyme
  • decrease in albumin, creatinine and urea
Apparent changes
  • There is an oestrogen-induced increase in several plasma binding proteins which apparently increases the levels of protein bound substances although their activity is unchanged as the free levels are unchanged. This may result in an elevation in plasma thyroxine, T4 > 200 nmol/L.

Investigation of the hirsute woman

Clinical evaluation

First line investigations

Second line investigations

long-standing hirsuties, regular menstrual cycles, no virilism

none necessary

 

long-standing hirsuties, irregular menstrual cycles, no virilism

investigate for PCO (ovarian ultra-sound or LH: FSH ratio). Testosterone >5.5 nmol/L

if Testosterone > 5.5 nmol/L proceed as below for CAH or tumour

severe hirsuties, irregular menstrual cycles and virilism

investigate for CAH if long history and for adrenal or ovarian androgen-secreting tumour if history is short

 


Page updated: 20/04/10 | Updated by: Dr. Julian Barth