Normal Prolactin Levels in a Five-Year-Old Girl
Normal prolactin levels in a 5-year-old girl should be interpreted using age-specific and sex-specific reference ranges, as prolactin concentrations are highest in the first 2 years of life, decrease to their lowest levels in mid-childhood (which includes age 5), and then rise again during adolescence. 1, 2
Age-Specific Considerations for Interpretation
A 5-year-old girl is in the mid-childhood period when prolactin levels are at their physiologic nadir, making this age group distinct from both early childhood and adolescence. 2
The Endocrine Society emphasizes that age-specific reference ranges must be used rather than adult reference values, as prolactin varies significantly across developmental stages. 1, 3
While adult non-pregnant women typically have upper limits around 20 μg/L (or approximately 425 mU/L), mid-childhood values are expected to be lower than adolescent or adult ranges. 2
Your laboratory's specific reference range for prepubertal children should guide interpretation, as assay methods vary between laboratories and can produce different numerical values. 1, 2
Clinical Context for Testing
Prolactin measurement in prepubertal children like a 5-year-old is typically indicated when evaluating growth failure, delayed puberty (though less relevant at age 5), headaches suggesting mass effect, or visual disturbances. 1
A single blood sample collected at any time of day is sufficient for initial assessment - specialized timing is not required. 1, 3
For modestly elevated levels, serial measurements should be considered to exclude stress-related elevation, which can increase prolactin up to five times the upper limit of normal. 1, 2
Important Diagnostic Pitfalls
Hyperprolactinemia is uncommon in prepubertal children, with 93% of pediatric prolactinomas presenting after age 12, making pathologic hyperprolactinemia rare at age 5. 1
If prolactin is elevated, medication review is essential as dopamine antagonists (including risperidone and other antipsychotics) are among the most common causes of hyperprolactinemia in children. 1, 2
Primary hypothyroidism must be excluded in any child with elevated prolactin, as it causes hyperprolactinemia in 40-43% of cases through compensatory thyrotropin-releasing hormone hypersecretion. 1, 2
Macroprolactinemia should be assessed when prolactin is mildly or incidentally elevated, as it accounts for 10-40% of hyperprolactinemia cases and represents biologically inactive prolactin complexes. 1, 2, 4
When to Pursue Further Evaluation
MRI imaging of the pituitary should be performed if prolactin levels are significantly elevated (typically >4,000 mU/L or 188 μg/L in pediatric populations with suspected prolactinomas) or if there are visual symptoms or signs of mass effect regardless of prolactin level. 3
The degree of prolactin elevation correlates with tumor size, though this is primarily relevant in adolescents rather than 5-year-olds given the rarity of prolactinomas in this age group. 1