What is free testosterone

testosterone is the male sex hormone, about 95% of which is produced in the Leydig cells of the testicle and 5% in the adrenal cortex in men.

In women, production takes place predominantly in the adrenal cortex.

Testosterone is synthesized from cholesterol. It is one of the fat-soluble hormones.
More than 40% of it is bound to the sex hormone binding globulin (SHBG) and more than 50% to albumin. Only about two percent are asfree testosterone (biologically active fraction).

Metabolism (Metabolism): In the androgen target tissue, the conversion into the more potent androgen dihydrotestosterone (DHT) usually takes place with the aid of the enzyme 5α-reductase.

Testosterone is subject to one circadian rhythm, that means in this case that it is poured out mainly in the morning (8.00-10.00 a.m.).

The procedure

Required material

Prepare the patient

  • The blood sample is taken in the morning (8 a.m. to 10 a.m.)
  • If necessary, take three blood samples in order to be able to carry out a determination from "pooled" serum

Disruptive factors

  • See Preparing the Patient

Normal values ​​women

genderAgeNormal values ​​in pg / ml
Female1st week of life (LW)< 9,74
 2nd-7th LW< 2,39
 2-3 Month of life (LM)< 2,41
 4th-5th LM< 0,4
 6-24 LM< 0,19
 2nd-7th Year of life (LJ)< 0,34
 8th-9th LJ0,55
 10-11 LJ< 1,02
 12-13 LJ0,56-1,37
 14.-15. LJ0,55-2,23 
 16.-17. LJ1,33-2,12 
 18.-39. LJ< 2,57
 40-59 LJ< 2,03
 > 60th LJ< 1,55

Normal values ​​men

genderAgeNormal values ​​in pg / ml
Male1st week of life (LW)5,27-11,8
 2nd-7th LW4,04-8,46
 2-3 Month of life (LM)1,32-5,06
 4th-5th LM< 2,68
 6-24 LM< 0,48
 2nd-7th Year of life (LJ)< 0,29
 8th-9th LJ0,79
 10-11 LJ0,1-9,0
 12-13 LJ3,5-9,0
 14.-15. LJ4,7-16,37
 16.-17. LJ8,76-19,41 
 18.-39. LJ8,8-27,0
 40-59 LJ7,2-23,0
 > 60th LJ5,6-19,0

Conversion factor

  • µg / L x 3.467 = nmol / L

Indications

  • Suspected hormonal disorders (hypogonadism; AGS; virilization (masculinization) of women)
  • Erectile dysfunction (erectile dysfunction)
  • Cryptorchidism
  • Therapy monitoring due to Testosterone Replacement Therapy
  • Suspected hormonally active tumors (e.g. testicular tumors; ovarian tumors)

interpretation

Interpretation of elevated values

Mrs

  • Adrenogenital Syndrome (AGS) - an autosomal recessive inherited metabolic disease characterized by disorders of hormone synthesis in the adrenal cortex. These disorders lead to a deficiency in aldosterone and cortisol.
  • Androgen-producing adrenal carcinoid
  • Hyperthyroidism (overactive thyroid) - leads to increased SHBG
  • Liver cirrhosis (connective tissue remodeling of the liver with functional impairment) - leads to increased SHBG
  • Menopause (menopause) - leads to increased SHBG
  • Cushing's disease - a disease caused by an excess of cortisol
  • Adrenal hypertrophy - overgrowth of the adrenal glands
  • Ovarian tumors (ovarian tumors)
  • Pubertas praecox - premature puberty
  • Pregnancy - leads to increased SHBG
  • Testosterone-producing tumor (testosterone levels> 1.2 ng / ml
  • Polycystic Ovarian Syndrome (PCO) - a gynecological condition associated with excessive cyst formation on the ovaries and an associated hormonal disorder

man

  • Hormone regulation disorders due to genetic defects (androgen resistance; androgen receptor defects)
  • Hormonally active tumors such as testicular tumors or androgen-producing adrenal carcinoma
  • Hyperthyroidism (overactive thyroid) - leads to increased SHBG
  • Liver cirrhosis (connective tissue remodeling of the liver with functional impairment) - leads to increased SHBG
  • Testosterone intake

Interpretation of lowered values

Mrs

  • Primary gonadal insufficiency (prepubertal; postmenopause)
  • Drug abuse (anabolic steroids)
  • Liver cirrhosis - connective tissue remodeling of the liver with functional impairment
  • Drug therapy with antiandrogens, estrogens or anabolic steroids
  • Addison's disease - adrenal insufficiency
  • Malnutrition (including anorexia nervosa)

man

  • Primary (hypergonadotropic) hypogonadism: e.g. B. Klinefelter syndrome (47, XXY or other variants)
    Note: The testosterone serum level is often in the middle to lower normal range for many years. The decrease in the testosterone serum level only occurs when the testicular secretion capacity decreases or the fibrosis increases. The gonadotropins in the serum are increased.
  • Secondary (hypogonadotropic) hypogonadism - gonadotropins decreased (LH ↓, FSH ↓)
  • Drug abuse (anabolic steroids)
  • Liver cirrhosis - connective tissue remodeling of the liver with functional impairment
  • Drug therapy with synthetic androgens, glucocorticoids, opioids
  • Malnutrition (including anorexia nervosa)

More information

  • Diseases that lead to increased SHBG synthesis, Since testosterone is mostly bound to SHBG (sex hormone binding hormone) in the serum, the free testosterone (biologically active fraction) decreases.
  • Man: Testosterone substitution therapy should not be initiated on the basis of a single low testosterone value without clinical evidence and clarification of the cause (see below andropause).
  • Atsymptomatic hypogonadism (Total Serum Testosterone Levels <12 nmol / l (3.5 ng / ml) There is a good chance that a testosterone substitution will improve the symptoms.
  • At total serum testosterone levels <8 nmol / l (231 ng / dl) is aThere is a need for therapy and it is likely; If the total testosterone serum level is between these values ​​(<12 nmol / l and <8 nmol / l), an indication for a trial therapy over 6-12 months with re-evaluation is given.

     
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