Luteinizing hormone (LH) is a gonadotropic hormone of the anterior pituitary gland that stimulates the secretion of sex hormones (estrogen and progesterone) in men and women. In men, LH acts on the Leydig cells of the testes, activating the synthesis of testosterone in them, in women – on the cells of the ovary membrane and the corpus luteum, stimulates ovulation and activates the synthesis of estrogens and progesterone in the ovarian cells. In the middle of the menstrual cycle, there is a rise in LH levels, which is preceded (for 12 hours) by a preovulatory peak of estradiol. Ovulation occurs 12-20 hours after reaching the maximum concentration of LH.
Luteinizing hormone consists of two subunits: alpha and beta. The alpha unit has a similar structure to other gonadotropic hormones (FSH, STH, TSH, etc.), but the beta element is unique, it is it that allows you to identify the hormone and determine its concentration. The synthesis of luteinizing hormone is stimulated by liberins of the hypothalamus, while statins, on the contrary, suppress its formation.
Causes of increased LH levels:
- dysfunction of the pituitary gland (including hyperpituitarism);
- primary dysfunction of the gonads;
- polycystic ovary syndrome;
- taking clomiphene, naloxone, spironolactone and anticonvulsants;
- hereditary disorders of sex chromosomes (Shereshevsky-Turner syndrome);
- testicular or pituitary tumors;
- Syndrome of premature puberty.
Reasons for lowering the level of LH:
- secondary insufficiency or tumors of the gonads;
- dysfunction of the hypothalamus and pituitary gland (hypopituitarism);
- galactorrhea-amenorrhea syndrome; anovulation; isolated deficiency of gonadotropic hormones associated with anosmia and hyposmia (Kallman’s syndrome); isolated deficiency of luteinizing hormone;
- taking certain drugs (progesterone, megestrol, digoxin, phenothiazine, large doses of estrogen);
- atrophy of the gonads in men after inflammation of the testicles due to mumps, gonorrhea, brucellosis; anorexia nervosa;
- syndrome of delayed growth and sexual development;
- severe stress or illness.
Luteinizing hormone: significance and functions
The role of luteinizing hormone cannot be overestimated. Together with FSH and other sex hormones, it affects the psycho-emotional behavior of men and women, affects the development and growth of the genital organs, promotes the formation of secondary sexual characteristics, affects sexual desire.
LH in women is involved in the formation of the follicle and stimulates the production of estrogen. Its high concentration in a woman causes the process of ovulation, and also contributes to the transition of the follicular phase to the luteal phase. Under the influence of LH, the ruptured follicle is converted into a corpus luteum, which produces progesterone, which is necessary during pregnancy. Progesterone, LH and other elements of the endocrine system create optimal conditions for the growth and development of the embryo.
A high concentration of LH in women lasts for about 14 days after ovulation, this period is necessary to maintain the functional activity of the corpus luteum before the production of hCG begins after successful implantation of the embryo. Then the need for large amounts of the hormone falls, which causes its decrease.
Luteinizing hormone in men plays an equally important role. It regulates the processes of spermatogenesis, development and adequate formation of the genital organs, stimulates the synthesis of testosterone. LH in men is more concentrated in the hair follicles, so their loss can be an alarming sign of the onset of hormonal imbalance.
Read Also: Hormone replacement therapy (HRT)
The rate of luteinizing hormone depends on gender, age, individual characteristics and other factors. Its level before puberty is quite low, but then its concentration increases markedly. The norm in men is relatively stable throughout life and ranges from 0.4-11 mIU / ml. But the norms of LH in women directly depend on the phase of the menstrual cycle and the state of the reproductive system.
In the follicular phase of the menstrual cycle, a gradual increase in the level of FSH is found in the blood, which has a direct effect on the growth and development of the follicles, but the formation of a full-fledged egg is impossible without luteinizing hormone, although its level is slightly lower. The norms for women in the first phase range from 2.4-12.6 mIU / ml.
After the full maturation of the follicle, a signal enters the pituitary gland, which provokes a large surge in the level of luteinizing hormone in women. During this period, maximum concentrations of FSH are also observed, together they contribute to the release of the egg from the dominant follicle (ovulation). During the ovulatory period, the norms of luteinizing hormone in women are 8.7-76.3 mIU / ml. It is worth noting that it is present not only in the blood, but in the urine; ovulation tests are based on this, allowing you to determine the most favorable time for conception.
After that, the luteal phase of the cycle begins and the transformation of the burst follicle into the corpus luteum occurs due to the presence of luteinizing hormone in the blood. During this period, there is a gradual decrease in its level, the norms are 0.5-16.9 mIU / ml. If pregnancy occurs, then the levels of LH and FSH remain low throughout the time, which makes it possible to slow down the maturation of follicles in the ovaries, the likelihood of ovulation and a new pregnancy. If there is no pregnancy, then the cycle repeats again, and the egg or unfixed embryo is removed along with the menstrual flow.
As reproductive function declines, ovarian reserve decreases, ovarian function is depleted, anovulatory menstrual cycles increasingly occur, and menopause occurs. The norms of luteinizing hormone in women during menopause range from 14 to 52.3 mIU / ml.
Indications for performing an analysis for LH
An analysis to determine the level of LH in men is carried out on any day in the morning on an empty stomach. LH in women is most often determined on days 3-8 or 19-21 of the cycle, but sometimes the study is performed throughout the cycle to assess the functioning of the reproductive system and the implementation of the IVF protocol.
The doctor prescribes this study in the following situations:
- Disorders of the menstrual cycle;
- Delayed or premature sexual development;
- growth retardation;
- Uterine bleeding;
- Decreased libido and potency;
- Excessive growth of body hair (hirsutism);
- Preparation for IVF;
- Control of hormone therapy;
- Definition of the ovulatory period.
You can take tests for this hormone and perform other diagnostic procedures at the IVF Center in Kaliningrad. After completing the analysis to determine the concentration of LH, you should not independently decipher the results of the study. Only a qualified specialist can adequately interpret the data, as well as take all necessary measures and draw up a further plan for diagnosis and treatment. In addition, the norms of different medical institutions may differ, because there are several methods for determining it, which affects the results of studies.
Luteinizing hormone: possible deviations
Hormonal imbalance of sex hormones leads to serious functional disorders of the reproductive system and the formation of pathological conditions. An increase in LH can be a sign of the following diseases:
- Ovarian exhaustion;
- polycystic ovary syndrome;
- Hypofunction of the testicles and ovaries;
- Surgical interventions in the gonads;
- Inflammatory diseases of the testicles and ovaries;
- Neoplasms of the pituitary gland;
- Excessive physical activity;
- Renal failure.
An increase in the normal level of the hormone can be recorded during menopause in women and after 60 years in men.
A decrease in the rate of luteinizing hormone in women may be a sign of pregnancy , but if it is not detected, then there is a high risk of pathology:
- The use of drugs;
- Neoplasms in the testicles or ovaries;
- Pathology of the pituitary or hypothalamus;
- Insufficiency of the luteal phase;
- stressful situations;
- hereditary diseases;
- Atrophy of the gonads, etc.
Hypofunction of the ovaries and a decrease in the rate of luteinizing hormone lead to insufficiency of the luteal phase. But what is this condition and why is it dangerous?
Insufficiency of the luteal phase primarily means a decrease in the functional activity of the corpus luteum, which leads to a decrease in the concentration of progesterone. Low levels of progesterone cannot fully prepare the body for a potential pregnancy, as a result of which the embryo cannot implant in the endometrium and is shed in menstrual blood.
Insufficiency of the luteal phase is especially dangerous in the first weeks of pregnancy, which arose against all expectations. This is due to the fact that the embryo cannot firmly gain a foothold in the endometrium, and as a result of the action of various negative factors, a miscarriage may occur at 2-4 months of pregnancy.