Reference Ranges
General guidelines for diagnosing prolactin excess (hyperprolactinemia) define the upper threshold of normal prolactin at 25 µg/L for women, and 20 µg/L for men. Similarly, guidelines for diagnosing prolactin deficiency (hypoprolactinemia) are defined as prolatin levels below 3 µg/L in women, and 5 µg/L in men. However, different assays and methods for measuring prolactin are employed by different laboratories, and as such the serum reference range for prolactin is often determined by the laboratory performing the measurement. Furthermore, prolactin levels also vary with, for example, age, sex, menstrual cycle stage, and pregnancy. The circumstances surrounding a given prolactin measurement (assay, patient condition, etc.) must therefore be considered before the measurement can be accurately interpreted.
The following chart illustrates the variations seen in normal prolactin measurements across different populations. Prolactin values were obtained from specific control groups of varying sizes using the IMMULITE assay.
| Proband | Prolactin, µg/L |
|---|---|
| women, follicular phase (n = 803) | 12.1 |
| women, luteal phase (n = 699) | 13.9 |
| women, mid-cycle (n = 53) | 17 |
| women, whole cycle (n = 1555) | 13.0 |
| women, pregnant, 1st trimester (n = 39) | 16 |
| women, pregnant, 2nd trimester (n = 52) | 49 |
| women, pregnant, 3rd trimester (n = 54) | 113 |
| Men, 21–30 (n = 50) | 9.2 |
| Men, 31–40 (n = 50) | 7.1 |
| Men, 41–50 (n = 50) | 7.0 |
| Men, 51–60 (n = 50) | 6.2 |
| Men, 61–70 (n = 50) | 6.9 |
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