Prevalence and Factors Associated with Hyperprolactinemia in Hospitalized Patients with Major Depressive Disorder

Imagine your brain as a bustling control tower, constantly sending out tiny chemical messengers to keep your body running smoothly. One of these messengers is called prolactin. Think of prolactin as the "milk manager" of your body. Its main job is to tell your body to make milk when you are a new parent, but it also hangs around doing other important chores, like helping with stress and keeping your bones strong. Usually, the brain keeps prolactin levels in a perfect, low-key zone. However, sometimes something goes wrong, and the "milk manager" gets overworked, causing levels to spike too high. This condition is called hyperprolactinemia. When this happens, it can cause headaches, trouble with periods, and even make people feel sad or anxious.

Now, enter Major Depressive Disorder (MDD). This is a serious kind of sadness that makes it hard to enjoy life, sleep, or eat. Doctors often treat MDD with medications that act like chemical keys, unlocking different parts of the brain to lift the mood. But here's the tricky part: some of these keys accidentally bump into the "milk manager" and make it work overtime. Other treatments, like a special machine that uses magnetic waves to zap the brain (called rTMS), might help fix things without causing this side effect. Scientists have long wondered: exactly how often does this "milk manager" go crazy in people with depression, and which specific treatments are the culprits? This is the mystery a team of researchers set out to solve.

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The Great Prolactin Detective Story

A team of researchers from the University of Electronic Science and Technology of China decided to play detective. They looked back at the medical records of 1,479 patients who were staying in a hospital in Chengdu, China, between January 2022 and December 2023. These patients were all between 18 and 60 years old and were there because they were struggling with Major Depressive Disorder. The researchers wanted to find out two things: How many of these patients had high prolactin levels, and what was causing it?

The Big Reveal: It's More Common Than You Think
The first thing the detectives found was that high prolactin was surprisingly common. Out of the 1,479 patients, 552 of them (which is 37.3%) had levels that were too high. That's more than one in every three patients! The researchers suspected that the mix of medications these patients were taking might be the reason, so they started sorting through the data to find the real villains and the heroes.

The Villains: The "Prolactin-Boosting" Pills
The study found that the type of medication a patient took was the biggest clue.

• Risperidone: This drug was the biggest troublemaker. Patients taking it were nearly 9 times more likely to have high prolactin than those who weren't.
• Olanzapine: This one was also a problem, making patients about 2.5 times more likely to have high levels.

Think of these two drugs like a heavy weight being dropped on the "milk manager's" desk, forcing them to work way too hard.

The Heroes: The "Prolactin-Sparing" Pills
But not all medications were bad news. The researchers found that some drugs actually helped keep prolactin levels down.

• Aripiprazole: This was the star of the show. Patients taking this drug were 93% less likely to have high prolactin. It's like a gentle hand that tells the "milk manager" to relax and go back to a normal pace.
• Quetiapine: This drug also helped, making high prolactin about 38% less likely.

The Other Clues: Age, Hormones, and Magnetic Waves
The detectives also found some other interesting patterns:

• Age: Younger patients were more likely to have high prolactin. As people got older, the risk went down.
• Thyroid Hormones: The study found a link between the thyroid gland and prolactin. Patients with higher levels of a hormone called TSH (Thyroid-Stimulating Hormone) and lower levels of FT4 (Free Thyroxine) were more likely to have high prolactin. It's as if a confused thyroid sends a signal that accidentally wakes up the "milk manager."
• Progesterone: This hormone, which is part of the body's reproductive system, was also slightly linked to higher prolactin levels.
• rTMS (The Magnetic Machine): Here is a fascinating discovery. Patients who received repetitive transcranial magnetic stimulation (rTMS)—a treatment that uses magnetic fields to stimulate the brain—were 36% less likely to have high prolactin. This was true even for patients who weren't taking any of the "villain" drugs. It suggests that this magnetic treatment might be a gentle way to treat depression without messing up the prolactin levels.

What About the Sadness Itself?
The researchers also checked if the sadness (depression) alone was causing the high prolactin. They looked at a group of 451 patients who were not taking any antipsychotic medications. Even in this group, younger age and not getting rTMS treatment were linked to higher prolactin. However, they found that the specific antidepressant drugs (the ones usually used just for sadness) did not seem to be the main cause of the high prolactin. It seems the depression itself, or the other medications, were the bigger players, not the standard antidepressants.

The Bottom Line
This study paints a clear picture: for people in the hospital with severe depression, high prolactin is a frequent side effect, happening in about 37.3% of cases. The main culprit is usually the specific type of antipsychotic medication they are taking. Drugs like risperidone and olanzapine tend to spike the levels, while aripiprazole and quetiapine seem to keep them safe. Interestingly, using magnetic brain stimulation (rTMS) might actually help lower the risk.

The researchers are careful to say that because this was a "look-back" study (looking at old records), they can't prove exactly why these things happen, but the patterns are very strong. They suggest that doctors should keep a close eye on prolactin levels when treating depression, especially if they are using certain medications, and maybe consider the magnetic treatment as a safer alternative for some patients.