From the Guidelines
Dopamine agonists, such as cabergoline, are the most common cause of decreased prolactin levels, as they reduce pituitary-origin hyperprolactinaemia of any cause. The use of dopamine agonists, particularly cabergoline, has been shown to induce normalization of prolactin levels in patients with prolactinoma, with a median of 68% of patients achieving normal prolactin levels 1. Other causes of decreased prolactin levels include pituitary gland damage or destruction, hypothyroidism, severe malnutrition or anorexia nervosa, and excessive exercise.
Some key points to consider when evaluating decreased prolactin levels include:
- Dopamine agonists, such as cabergoline, are effective in reducing prolactin levels and are the first-line treatment for prolactinoma 1
- Pituitary gland damage or destruction can lead to decreased prolactin production, which can be a sign of broader pituitary dysfunction
- Hypothyroidism can sometimes lead to decreased prolactin levels, although it is more commonly associated with hyperprolactinemia 1
- Severe malnutrition or anorexia nervosa can disrupt hormonal balance, leading to decreased prolactin levels
- Excessive exercise may also reduce prolactin levels in some individuals
It's essential to note that low prolactin levels are generally only clinically significant in women who are trying to breastfeed, as prolactin is the primary hormone responsible for milk production. In other populations, low prolactin typically doesn't require treatment unless it's a sign of broader pituitary dysfunction. The diagnosis of hyperprolactinemia or hypoprolactinemia requires age-specific and sex-specific prolactin reference ranges and the exclusion of confounding conditions such as hypothyroidism, renal and/or hepatic impairment, and use of medications that cause hyperprolactinemia 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. Cabergoline is a long-acting dopamine receptor agonist with a high affinity for D2 receptors Results of in vitro studies demonstrate that cabergoline exerts a direct inhibitory effect on the secretion of prolactin by rat pituitary lactotrophs.
The cause of decreased prolactin levels is the inhibitory effect of dopamine on the secretion of prolactin by the anterior pituitary, which can be enhanced by dopamine receptor agonists such as cabergoline 2.
- Dopamine inhibits the secretion of prolactin by the anterior pituitary.
- Cabergoline, a long-acting dopamine receptor agonist, decreases serum prolactin levels by exerting a direct inhibitory effect on the secretion of prolactin.
From the Research
Causes of Decreased Prolactin Level
- Dopamine inhibitory control: Prolactin (PRL) is secreted by the lactotroph cells in the anterior pituitary gland, which is under inhibitory control of dopamine 3.
- Dopaminergic drugs: Dopaminergic drugs such as cabergoline and bromocriptine can decrease prolactin levels by inhibiting prolactin secretion 4, 5.
- Treatment of hyperprolactinemia: Cabergoline and bromocriptine are used to treat hyperprolactinemia, and they can decrease prolactin levels to normal or even below normal levels 4, 5, 6.
Effects of Decreased Prolactin Level
- Failure of lactation: Decreased prolactin levels can cause failure of lactation, as prolactin is essential for milk synthesis and secretion 3, 7.
- Metabolic abnormalities: Decreased prolactin levels have been associated with metabolic abnormalities, including insulin resistance, abnormal lipid profile, obesity, and sexual dysfunction 3, 7, 6.
Comparison of Dopaminergic Drugs
- Cabergoline vs bromocriptine: Cabergoline has been shown to be more effective than bromocriptine in decreasing prolactin levels and improving metabolic and cardiovascular risk factors 4, 6.
- Tolerability: Cabergoline is generally better tolerated than bromocriptine, with fewer adverse events reported 4, 5, 6.