Prolactin in serum
Apr 26, 2018
Prolactin is synthesized in specialized lactogenic cells of the anterior lobe of the pituitary gland;its synthesis and release is under the stimulatory-inhibitory influence of the hypothalamus. The hormone is secreted sporadically. In addition to the pituitary gland, prolactin is synthesized by the decidual membrane( which explains the presence of prolactin in the amniotic fluid) and endometrium.
Unlike gonadotropins, prolactin consists of a single peptide chain comprising 198 amino acid residues, and has a molecular weight of approximately 22,000-23,000. The target organ for prolactin is the mammary gland, the development and differentiation of which is stimulated by this hormone. During pregnancy, the concentration of prolactin rises due to the enhanced formation of estrogen and progesterone. The stimulating effect of prolactin on the mammary gland leads to postpartum lactation.
High concentrations of prolactin have an inhibitory effect on ovarian steroidogenesis, the formation and secretion of gonadotropins by the pituitary gland. In men, its function is not known.
Prolactin appears in serum in three different forms. Biologically and immunologically active monomeric( small) form predominates( approximately 80%), 5-20% is present in the form of a biologically inactive dimer( "large") form and 0.5-5% in the form of a tetrameric( "very large") form, which has a low biological activity. Reference values for the concentration of monomeric form( biologically active) prolactin in the blood are presented in the table.
Prolactin production and secretion of lactotrophic a-cells of the anterior pituitary gland is under the control of a number of regulatory centers of the hypothalamus. Dopamine has a pronounced oppressive effect on the secretion of prolactin. The release of dopamine by the hypothalamus is controlled by the nucleus dorsomedialis. In addition to dopamine, norepinephrine, acetylcholine and y-aminobutyric acid have an inhibitory effect on the secretion of prolactin. Derivatives of TRH and tryptophan, such as serotonin and melatonin, perform the function of the PRG and have a stimulating effect on the secretion of prolactin. Concentration of prolactin in the blood increases during sleep, exercise, hypoglycemia, lactation, pregnancy, under stress( surgery).
Hyperprolactinemia( in men and women) is one of the main causes of fertility disorders. Prolactin is used in clinical practice in anovulatory cycles, hyperprolactinemic amenorrhea and galactorrhea, gynecomastia and azoospermia. Prolactin is also determined for suspected breast cancer and pituitary tumors.
In determining prolactin, remember that the concentration depends on the time taken for blood, since prolactin secretion occurs sporadically and is subject to a 24-hour cycle. Prolactin release is stimulated by breastfeeding and stress. In addition, increasing concentrations of prolactin in the serum causes a number of drugs( for example, benzodiazepines, phenothiazines), TRH and estrogens. The secretion of prolactin is inhibited by derivatives of dopamine( levodopa) and ergotamine.
Recently, many authors have reported the presence of macroprolactin in the blood of women with various endocrine diseases or during pregnancy. It is also described that there is a different ratio of serum macro-prolactin( "very large" - a molecular weight of more than 160,000) and monomeric prolactin when analyzed by different test systems. A number of test systems collectively determine all variants of the prolactin molecule in a wide range. This circumstance can lead to different results depending on the test system used.
Blood samples with elevated prolactin levels may contain macro-prolactin( prolactin-IgG complex) and oligomeric forms of the hormone. Patients with prolactin levels above the reference values should differentiate different forms of the hormone. Macro-prolactin or prolactin oligomers are determined by pretreating a serum sample with a 25% polyethylene glycol solution( PEG-6000) and then analyzing the supernatant for prolactin. The discrepancy between the prolactin values in the treated and native samples indicates the presence of macroliprolactin and / or oligomers of prolactin.
The amount of macroprolactin and its oligomers is determined by calculating the ratio of prolactin concentration in the initial sample and after PEG precipitation - [(prolactin concentration after PEG precipitation) / 100% prolactin concentration in the initial sample( before PEG precipitation)].The result of the study is evaluated as follows.
- If the ratio exceeds 60% - the sample mainly contains monomeric prolactin.
- Values 40-60%( "gray zone") - the sample contains both monomeric prolactin and macro-prolactin and / or oligomers of prolactin. You should inform the clinician that you need to re-examine the patient's blood( for example, by filtration chromatography in a gel or another test system).
- A ratio of less than 40% indicates that the sample contains macroprolactin and / or prolactin oligomers. The result should be compared with clinical data.
To date, the clinical significance of various forms of prolactin remains unclear.
Low prolactin level
Low levels of prolactin in the blood are normal in children, non-pregnant women and men. The expressed decrease in prolactin level, as a rule, does not require special treatment. However, if a low level of prolactin and other hormones( for example, thyroid hormones) is detected, an additional examination should be performed to exclude the pituitary disease:
- Benign and malignant tumors of the pituitary gland.
- Pituitary tuberculosis.
- Head trauma with impaired pituitary function.
- Conditions after radiotherapy of pituitary tumors.
- Reduction of prolactin in the blood occurs with long-term medication: Levodopa, Dopamine and some others.
Symptoms of increased prolactin in women
Menstrual irregularities: amenorrhea, oligomenorrhea. That is, menstruation is very rare or nonexistent. This is the most common symptom. Occurs in 60-90% of cases. Approximately every fifth woman reports that menstruation from the very beginning were irregular, the time of onset was always somewhat delayed. Also, the development of amenorrhea often coincides with the onset of sexual activity, the abolition of oral contraceptives, abortions, childbirth, surgeries, the introduction of intrauterine spirals.
Infertility is associated with the lack of ovulation or shortening of the luteal phase( 2 phases of the cycle).Sometimes women have miscarriages in the early stages of pregnancy( 8-10 weeks).
The galactorrhea, i.e.the allocation of milk from the nipples of the mammary glands. It occurs in about 70% of cases. The longer the disease, the less galactorrhea becomes. Distinguish the degree of galactorrhea: 1 degree - single drops with strong pressure on the nipple, 2 degree - jet or copious drops with slight pressure, 3 degree - spontaneous separation of milk.
Decreased libido, lack of orgasm, frigidity.
Hirsutism and acne are noted in 20-25% of women, i.e.excess hair growth on the face, around the nipples and along the white line of the abdomen.
Symptoms of increased prolactin in men
Decrease or absence of libido and potency. The most frequent complaint is found in 50-85% of cases. It is with her that men first seek medical help.
Reduction of secondary sexual characteristics. Reduction of hair loss occurs in 2-21% of men.
Infertility due to oligospermia in 3-15%.Infertility occurs much less often than in women, and so these men rarely seek help.
Gynecomastia occurs in 6-23% of men. Gynecomastia is a benign enlargement of the mammary glands in men. Externally, the breast looks like a female breast of small size. There is a true and false gynecomastia.
When hyperprolactinaemia occurs, the true, which is associated with an increase in the mammary gland itself. False gynecomastia is associated with the deposition of fat in the subcutaneous tissue.
Treatment of increased prolactin
In the treatment of increased prolactin a good prognosis.
What is done with a tumor in the anterior pituitary gland? Everything depends on its size and the specific situation of the patient.
Men for the treatment of increased prolactin are most often offered surgery, as they discover an adenoma at a later date, and it grows more active. At large sizes, the tumor can squeeze the optic nerves and become a threat to vision.
This can happen in women, although they have benign and small adenoma grows very slowly or does not grow at all. A drug sorceress-ergot-bromocriptine, better known in our country as a parodel, has the ability not only to reduce and normalize the level of prolactin, but also to destroy, at least reduce the size of the tumor. Therefore, treatment, as a rule, begins with the appointment of a parlodel, even for men. The drug helps to significantly reduce the tumor before surgery so that it is easier for surgeons to remove it.
Currently, not only the parlodel of the company "Sandoz", but also a wonderful domestic drug from ergot - abergin is used. Available to our patients are analogues of the parlodel - bromergone, corrected.
A woman, if she tolerates the drug well and she does not have a threat of vision due to pituitary adenoma, can take the medicine for a long time, up to 3 years, with interruptions. Many successfully give birth, taking parlodel and only thanks to him. Well, then? Violations of the menstrual cycle can be repeated. Do I need to continue taking the medicine?
If a woman wants to give birth, if she is concerned about the decreased libido caused by increased prolactin, the lack of orgasm, the dryness of the vagina, the overweight, the treatment continues. But some patients who do not like to be treated gently and for a long time, believe that the irregularity of menstruation does not interfere with them. In such cases, after consultation with a doctor, you can and refuse from the parlodel. But keep in mind that over time, a significant excess of prolactin and related cycle disorders can lead to increased brittleness of the bones.
Prophylaxis of increased prolactin
There are no specific measures to prevent elevated prolactin. The most common recommendations: do not abuse medicines, it's best not to sunbathe - after all, insolation stimulates the hypothalamus, and he in turn pituitary. ..
Women who have discovered lactorrhea( excretion from the breast), do not squeeze the contents out of the nipple. This only stimulates the production of prolactin. More often it's just the individual sensitivity of the breast tissue to the normal level of the hormone, but, constantly pressing on the nipple, you are pushing the process of increasing prolactin.
Small discharge from the breast during 2 to 3 years after childbirth or abortion is within normal limits. And only if in the absence of pregnancy and menstruation there are these secretions, prolactin must be checked necessarily. In any case - to consult with a doctor, because allocation can serve as a signal and some other trouble.