PCOS (hormonal measurements in suspected PCOS)

Initial hormonal investigation should aim at excluding disorders of hypothalmic-pituitary-ovarian axis that cause ovulation disturbance. Measurements should ideally occur in the first week of the menstrual cycle and include:

• testosterone, sex binding globulin, FSH, LH, PRL, TFTs

A diagnosis of PCOS is supported by:

• elevated free testosterone levels (in saliva or plasma)
  
  
• low levels of sex hormone binding globulin
  • to calculate the free androgen index (FAI), total testosterone value x 100 is divided by the sex hormone binding globulin value (1)
  • FAI levels of 5 and above are indicative for polycystic ovary syndrome (2)
    • other disorders presenting with clinical and/or biochemical signs of hyperandrogenism such as congenital adrenal hyperplasia, androgen-secreting tumours or Cushing syndrome should be excluded. For this purpose further laboratory testing, e.g. 17-OH-progesterone, follicle-stimulating hormone, oestradiol, prolactin or cortisol may be necessary
      
      
• elevated LH:FSH ratio - usually, to more than 3:1; serum LH is raised with that of FSH relatively lower than in a normal menstrual cycle; measure in the first week of the menstrual cycle
  • however, an elevated LH:FSH ratio is no longer considered to be a diagnostic criterion for PCOS due to its inconsistency (1)
    
    
• there may also be elevated androstenedione levels and high circulating levels of oestrone

Note that serum testosterone levels in patients with PCOS seldom exceed 4.8 nmol/l. If testosterone levels are greater than 4.8 nmol/l then further endocrinological investigation to exclude other causes of androgen hypersecretion (e.g. Cushing's syndrome, adrenal gland or ovarian tumours) (3).

Reference:

• 1. RCOG (2007) Long-term consequences of polycystic ovary syndrome.
• 2.Blume-Peytavi U et al. S1 guideline for diagnostic evaluation in androgenetic alopecia in men, women and adolescents. Br J Dermatol. 2011;164(1):5-15
• 3. Balen AH et al (1995). Polycystic ovary syndrome: the spectrum of the disorder in 1741 patients. Hum Reprod, 10, 2107-11.