Testosterone in the blood

Testosterone is an androgenic hormone responsible for secondary sexual characteristics in men. The most important source of testosterone is Leidig cells of the testes. Testosterone supports spermatogenesis, stimulates the growth and function of additional sexual glands, as well as the development of the penis and scrotum. The hormone has an anabolic effect, mainly in relation to bones and muscles. Due to direct effects on the bone marrow, as well as by activating the synthesis of erythropoietin in the kidneys, testosterone stimulates erythropoiesis. A hormone is also needed to maintain libido and potency. The synthesis of testosterone is controlled by the LH of the anterior lobe of the pituitary gland. In men, this is the main androgen, which determines the achievement of sexual maturity. The concentration of the hormone in the blood increases after exercise. The reference values of serum testosterone concentration are given in Table. 9-28.

In adult healthy men, peak testosterone concentrations occur in the morning and decrease by at least 25% in the evening. After 50 years, there is a progressive decrease in testosterone in the blood.

The concentration of testosterone in the blood serum increases with idiopathic premature puberty and hyperplasia of the adrenal cortex in boys, tumors of the adrenal cortex, extragonadal tumors in men, in diseases of trophoblast in pregnant women, and arrenoblastomas.

Reduction of testosterone concentration in the blood is noted with Down's syndrome, delayed puberty.

Reference values (norm) of testosterone concentration in blood serum

Age	Floor	Testosterone
		Ng / dL	Nmol / l
Newborns	Male	75-400	2.6-13.9
	Women's	20-64	0.69-2.22
Prepubertal age:
1-5 months	Male	1-177	0.03-6.14
	Women's	1-5	0.03-0.17
6-11 months	Male	2-7	0.07-0.24
	Women's	2-5	0.07-0.17
1-5 years	Male	2-25	0.07-0.87
	Women's	2-10	0.07-0.35
6-9 years	Male	3-30	0.10-1.04
	Women's	2-20	0.07-0.69
Pubertal age:
1 age group	Male	2-23	0.07-0.80
	Women's	2-10	0.07-0.35
2 age group	Male	5-70	0.17-2.43
	Women's	5-30	0.17-1.04
3 age group	Male	15-280	0.52-9.72
	Women's	10-30	0.35-1.04
4 age group	Male	105-545	3.64-18.91
	Women's	15-40	0.52-1.39
5 age group	Male	265-800	9.19-27.76
	Women's	10-40	0.35-1.39
Adults	Male	280-1100	8.72-38.17
	Women's	15-70	0.52-2.43
Pregnant	3-4 times higher than usual concentration
Postmenopause		8-35	0.28-1.22

Approximately 2% of testosterone circulating in the blood is in a free state. Only free testosterone is able to penetrate the cell, bind to intracellular receptors, penetrate the nucleus and change gene transcription (that is, ultimately to realize its biological effects).

Reference values (norm) of concentration of free testosterone in blood serum

	Floor	Free testosterone
Age		Pg / ml	PMol / l
Newborns	Male	1.5-31	5.2-107.5
	Women's	0.5-2.5	1.7-8.7
1-3 months	Male	3.3-8	11.5-62.7
	Women's	0.1-1.3	0.3-4.5
3-5 months	Male	0.7-14	2.4-48.6
	Women's	0.3-1.1	1.0-3.8
5-7 months	Male	0.4-4.8	1.4-16.6
	Women's	0.2-0.6	0.7-2.1
Children:
6-9 years	Male	0.1-3.2	0.3-11.1
	Women's	0.1-0.9	0.3-3.1
10-11 years old	Male	0.6-5.7	2.1-9.8
	Women's	1.0-5.2	3.5-18
12-14 years old	Male	1.4-156	4.9-541
	Women's	1.0-5.2	3.5-18
15-17 years old	Male	80-159	278-552
	Women's	1-5.2	3.5-18
Adults	Male	50-210	174-729
	Women's	1.0-8.5	3.5-29.5

Free testosterone is independent of the concentration of SSH. Therefore, the determination of free testosterone is indicated in those situations when the content of the SSH may increase (hyperthyroidism, hyperestrogenism, pregnancy, intake of oral contraceptives or antiepileptic drugs) or decrease (hypothyroidism, obesity).