Related tests: SHBG, total testosterone

Clinical significanceClinical indicationsSample typePreparationNotes

Clinical significance
Circulating testosterone is present both in free form and bound to SHBG (sex hormone-binding globulin); the free form is independent of changes in SHBG concentration, so free testosterone is more appropriate than total testosterone when SHBG is increased (hyperthyroidism, pregnancy, oral contraceptives, anti-epileptic drugs) or decreased (hypothyroidism, obesity).

Clinical indications
In men, assessment of hormonal function; in women, hirsutism and polycystic ovary syndrome.

Sample type
The patient must have a blood sample taken.

Preparation
You must fast for at least 8 hours; a small amount of water is allowed.

Notes
Reference values vary during:

  • Ovulation: 0.00 – 4.10 pg/mL
  • Menopause: 0.10 – 1.70 pg/mL
  • Oral contraceptives: 0.30 – 2.00 pg/mL