Prolactin is a peptide hormone produced primarily by the pituitary gland, a small endocrine organ located at the base of the brain. An abnormally high concentration of this hormone in the bloodstream is known as hyperprolactinemia. This hormonal imbalance can lead to various symptoms affecting reproductive health and has been linked to changes in hair growth. Understanding whether elevated prolactin levels cause hair loss requires examining the hormone’s influence on the hair follicle cycle.
Prolactin’s Primary Functions
The most recognized role of prolactin is in reproduction, specifically stimulating milk production (lactation) following childbirth. It also contributes to breast tissue development during pregnancy. In males, the hormone regulates testosterone production and supports overall reproductive function.
Beyond reproduction, prolactin helps maintain overall balance. It is involved in regulating the immune system and influencing immune cell function. The hormone also helps maintain the body’s water and salt balance and is implicated in aspects of metabolism.
How Elevated Prolactin Disrupts Hair Growth
Hyperprolactinemia interferes with the normal, cyclical process of hair growth by directly affecting the hair follicle. The hair cycle has three main phases: anagen (growth), catagen (regression), and telogen (rest and shedding). Prolactin acts as an inhibitory signal, prematurely pushing the hair follicle out of the active anagen growth phase.
Studies using human scalp hair follicles show that high doses of prolactin significantly inhibit hair shaft elongation. This hormonal signal forces the follicles into an early catagen-like stage, the transitional phase where growth stops. This premature shift disrupts the natural timing of the cycle, leading to an increased number of hairs entering the telogen or shedding phase.
The mechanism involves a decrease in cell proliferation and an increase in apoptosis, or programmed cell death, within the hair bulb keratinocytes. This localized cell death at the base of the hair follicle shortens its lifespan and causes the hair to be shed earlier than normal. The resulting hair thinning is often diffuse, similar to telogen effluvium, or sometimes presents as an androgenetic alopecia-like pattern.
Common Reasons for High Prolactin Levels
The causes of hyperprolactinemia are categorized into physiological, pharmacological, and pathological factors.
Physiological Causes
Prolactin levels naturally rise during pregnancy and breastfeeding. Other temporary, non-disease causes include intense physical exercise, severe stress, nipple stimulation, and post-meal spikes.
Pathological Causes
Pathological causes involve underlying medical conditions. The most common is a prolactinoma, a benign tumor of the pituitary gland that autonomously produces excess prolactin. Other health conditions like hypothyroidism, chronic kidney disease, liver cirrhosis, or polycystic ovary syndrome (PCOS) can also lead to elevated prolactin levels.
Pharmacological Causes
Many common prescription medications increase prolactin by interfering with the brain’s regulatory system, which uses dopamine to suppress prolactin release. These include certain antipsychotic medications, some antidepressants, specific drugs used for high blood pressure, and medications for nausea or heartburn. If a clear cause cannot be identified, the situation is referred to as idiopathic hyperprolactinemia.
Testing and Treatment Approaches
If hair loss is accompanied by other symptoms of hyperprolactinemia, such as irregular menstrual periods, galactorrhea (milk discharge not related to nursing), or low sex drive, a medical evaluation is warranted. Diagnosis begins with a blood test to measure the serum prolactin level, typically done while fasting, to confirm hyperprolactinemia.
Further blood work includes measuring thyroid-stimulating hormone (TSH) to rule out hypothyroidism. If prolactin levels are significantly elevated, a magnetic resonance imaging (MRI) scan of the brain is often ordered to check for a pituitary tumor, such as a prolactinoma.
The treatment approach depends entirely on the identified cause. If a medication is the culprit, the doctor may adjust the dose or switch to an alternative drug. For prolactinomas or cases where no other cause is found, the standard treatment involves dopamine agonists, such as cabergoline or bromocriptine. These drugs mimic dopamine, effectively lowering prolactin levels and shrinking the tumor, which often resolves associated symptoms like hair loss.