What is prolactin and its role in the body?

From the Guidelines

Prolactin is a hormone that plays a crucial role in various bodily functions, including lactation, reproductive function, immune system regulation, and metabolism, and its abnormal levels can lead to health issues such as irregular menstrual cycles, infertility, and decreased libido. Prolactin is primarily produced by the pituitary gland in the brain and serves several important functions in the human body. Its most well-known role is stimulating milk production in women after childbirth, enabling breastfeeding through a process called lactation. During pregnancy, prolactin levels rise steadily to prepare the mammary glands, but actual milk production is suppressed by high estrogen and progesterone until after delivery.

Key Functions of Prolactin

• Influences reproductive function in both men and women by affecting the production of sex hormones
• Plays a role in immune system regulation, helping with immune cell development and function
• Contributes to metabolism by affecting insulin sensitivity and fat storage
• Helps maintain sperm production and testosterone levels in men

Health Issues Associated with Abnormal Prolactin Levels

• Elevated levels (hyperprolactinemia) may lead to irregular menstrual cycles, infertility, decreased libido, and inappropriate milk production
• May require treatment with medications like bromocriptine or cabergoline if symptomatic or caused by a pituitary tumor, as recommended by recent guidelines 1

Diagnosis and Management of Prolactin-Related Disorders

• Serum prolactin measurement is recommended in children and young people (CYP) presenting with signs and symptoms such as delayed puberty, galactorrhoea, visual field loss, growth or pubertal arrest, or menstrual disturbance 1
• Cabergoline is recommended as first-line therapy for CYP with prolactinoma, even in the presence of visual disturbance and pituitary apoplexy, while carefully monitoring for any deterioration in vision, pituitary function, or general status 1

From the FDA Drug Label

The secretion of prolactin by the anterior pituitary is mainly under hypothalamic inhibitory control, likely exerted through release of dopamine by tuberoinfundibular neurons.

• Prolactin is a hormone secreted by the anterior pituitary gland.
• Its secretion is mainly under hypothalamic inhibitory control, which means that the hypothalamus helps to regulate its release.
• Dopamine plays a key role in this regulation, as it is released by tuberoinfundibular neurons to inhibit prolactin secretion.
• In simple terms, prolactin is a hormone that is controlled by the brain and plays a role in various bodily functions, including lactation and reproductive processes 2.

From the Research

What is Prolactin

• Prolactin is a polypeptidic hormone secreted by the anterior pituitary gland 3
• It is also produced by many extrapituitary cells, including the central nervous system, the immune system, the uterus, and the mammary gland itself 4
• Prolactin exists in three heterogenic forms, with the monomer being the principal biologically active form 5

Role of Prolactin in the Body

• Prolactin plays a crucial role in lactation during pregnancy and breastfeeding 3, 5
• It stimulates the growth of the mammary gland and the production of milk 5
• Prolactin also has other biological functions, including:
  • Angiogenesis (formation of new blood vessels) 6
  • Immunoregulation (regulation of the immune system) 6
  • Osmoregulation (regulation of water and electrolyte balance) 6
  • Cell growth and differentiation 7

Regulation of Prolactin Secretion

• Prolactin secretion is regulated by the hypothalamic-pituitary axis, with dopamine providing inhibitory control 3, 4
• Other factors, such as stress, light, audition, and olfaction, can also stimulate prolactin secretion 4
• Prolactin levels decrease as lactation is established, but nursing stimulates prolactin release from the pituitary, promoting continued milk production 5

Pathological Conditions Associated with Prolactin

• Hyperprolactinemia (elevated prolactin levels) can cause reproductive dysfunction, infertility, and galactorrhea (spontaneous milk production) 3, 6
• Lactotroph adenomas (prolactinomas) are a common cause of hyperprolactinemia, representing approximately 40% of all pituitary tumors 6
• Prolactin has also been implicated in the development and progression of certain types of cancer, including gynecological cancers 7