"Shen-Mi"'s series of popular science on pituitary tumors: What type of elevated prolactin do you have? (Part 1)

1. Doctor, I went to the hospital for some tests because I am trying to get pregnant recently. One of the six sex hormones, prolactin, was elevated. What is the cause of this? Is it serious? Will it affect my pregnancy?

2. Doctor, I found milky white liquid coming out of my breasts when I was taking a shower a few days ago. I went to see a breast surgeon and they checked six sex hormones for me. They found that my prolactin was high and recommended that I go to the endocrinology department. What disease do I have? I haven’t married or had children yet!

3. Doctor, I haven’t had my period for 2 months. I went to the gynecology department for a checkup 3 days ago and the doctor said my prolactin level was elevated. She asked me to see the endocrinology department. I searched on Baidu and it said I had a pituitary tumor. Is it serious? Do I need surgery?

4. Doctor, I have been feeling a bit lackluster these past few months, and I no longer have morning erections. I went to see an andrologist, who checked my sex hormones and found that my prolactin level was extremely high. What disease do I have?

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The above scenarios are common medical problems encountered in outpatient clinics. This popular science article will answer your questions and provide detailed introduction to a series of issues about "prolactin".

1. About prolactin

Prolactin (PRL), also known as prolactin, is a hormone secreted by the anterior pituitary gland. As its name suggests, its main function is to promote the development and growth of breast secretory tissue, initiate and maintain lactation, and it can also affect gonadal function and inhibit ovulation.

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The secretion of prolactin is pulsatile and has a circadian rhythm . It gradually increases after falling asleep, reaches a peak 1-2 hours before waking up in the morning, and drops rapidly after waking up. Therefore, during the day, the human body's prolactin level reaches the physiological maximum value between 4 and 6 in the morning and the physiological minimum value between 9 and 11 in the morning. The values ​​measured at different times are different.

The secretion of prolactin by pituitary lactotroph cells is directed and regulated by its leader, the hypothalamus. Under normal circumstances, the hypothalamus secretes both prolactin release inhibitory factors (PIFs) and prolactin releasing factors (PRFs), with the regulation of PIFs being dominant. As the name implies, PIFs inhibit the secretion of prolactin, while PRFs promote the secretion of prolactin. The two are in a dynamic equilibrium state. When this balance is broken for some reason, "hyperprolactinemia" will appear.

2. About Hyperprolactinemia

1. Definition: Hyperprolactinemia refers to a state in which the peripheral serum PRL level is persistently higher than the normal value due to various reasons.

2. Common causes: can be divided into four categories: physiological, pharmacological, pathological and idiopathic.

1) Physiological reasons

Many physiological factors can affect PRL levels, and serum PRL levels can also change in different physiological periods, such as stress states (including tension, cold, physical exercise, sexual behavior, hypoglycemia, mental trauma, etc.), high-fat and high-protein diets , sleep day and night reversal , mid-menstrual cycle , as well as pregnancy, lactation, and the neonatal period .

2) Drug factors

Many drugs can cause hyperprolactinemia, most of which are caused by antagonizing hypothalamic PIFs or enhancing PRFs. A few drugs may have a direct effect on PRL cells, as listed below:

Image source: Reference 1

3) Pathological causes

Ø Hypothalamic diseases: craniopharyngioma, inflammation

Ø Pituitary disease: The most common cause is pituitary prolactin adenoma. Other causes such as growth hormone adenoma and adrenocorticotropic hormone adenoma can also cause PRL elevation.

Ø Primary hypothyroidism

Ø Chronic renal insufficiency

Ø Chest diseases: trauma, surgery, burns, herpes zoster

Ø Gynecological and obstetric surgery: artificial abortion, induced labor, stillbirth, hysterectomy, tubal ligation, oophorectomy, etc.

Ø Polycystic ovary syndrome (PCOS)

4) Idiopathic hyperprolactinemia: It can only be considered after excluding the above factors, and close clinical follow-up is required.

3. Comparison of the degree of increase in prolactin levels caused by different reasons

In clinical practice, doctors can make a preliminary differential diagnosis based on the degree of prolactin elevation.

Image source: Up To Date

4. What symptoms may result from elevated prolactin?

1) Female: Menstrual disorders, amenorrhea, infertility; galactorrhea; weight gain, bone loss or osteoporosis

2) Male: erectile dysfunction, loss of libido, infertility; breast development, galactorrhea; loss of secondary sexual characteristics (such as reduced beard, small and soft testicles, etc.), bone loss or osteoporosis

3) Symptoms of tumor compression: Prolactinoma is the most common cause of pathological hyperprolactinemia. The clinical manifestations of tumor occupation include headache, decreased vision, visual field defects and other cranial nerve compression symptoms. A small number of patients develop acute pituitary stroke, manifested by sudden severe headache, vomiting, decreased vision, oculomotor nerve paralysis, and even coma.

So, what should you do if you find that your prolactin level is elevated? Stay tuned for the next article!

【References】

1. Endocrinology Group of the Chinese Society of Obstetrics and Gynecology. Consensus on the diagnosis and treatment of hyperprolactinemia in women. Chinese Journal of Obstetrics and Gynecology, 2016, 51(3):161-168.

2. Melmed S, Casanueva FF, Hoffman AR, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society ClinicalPractice Guideline. J Clin Endocrinol Metab, 2011, 96(2):273-288.

3. Freeman ME, Kanyicska B, Lerant A, Nagy G. Prolactin: structure, function, and regulation of secretion. Physilo Rev, 2000,80(4):1523-1631.