From the Guidelines
Prolactin levels can be sent at any time of day, as a single blood sample collected at any time is sufficient to assess hyperprolactinaemia. According to the consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence, a single prolactin measurement taken at any time of the day is sufficient to assess hyperprolactinaemia 1. This is because prolactin secretion also rises in response to stress, and sampling can be repeated on a different day with two or three samples at 20–60 min intervals to differentiate stress-related hyperprolactinaemia from organic disease.
Some key considerations when interpreting prolactin levels include:
- Age-specific and sex-specific prolactin reference ranges are required for accurate diagnosis 1
- Confounding conditions such as hypothyroidism, renal and/or hepatic impairment, and use of medications that cause hyperprolactinaemia must be excluded 1
- Serum prolactin concentrations vary with age and sex, with highest levels in the first 2 years of life and lower levels in mid-childhood, rising again in adolescence 1
It is also important to note that unexplained, persistently mildly or moderately elevated prolactin in blood samples taken after rest could be due to the stalk effect (disconnection hyperprolactinaemia, pituitary stalk compression from mass lesions disrupting the dopaminergic inhibition of lactotroph cells) 1. Therefore, a single prolactin measurement at any time of day can be used as an initial assessment, but further evaluation and consideration of these factors may be necessary for accurate diagnosis and management.
From the Research
Prolactin Level Measurement
- Prolactin levels can be measured at any time, but it is recommended to draw blood samples in the morning with the patient in a fasting state to ensure accurate results 2.
- Serum prolactin levels can rise rapidly during pregnancy and lactation, and can also be affected by various physiological and pharmacological factors 3.
- In children, an elevated morning prolactin concentration does not always mean hyperprolactinemia, and a circadian prolactin secretion profile should be performed to avoid overdiagnosis 4.
Timing of Prolactin Measurement
- There is no significant difference in prolactin levels measured in the morning after a typical night's sleep and in the morning after a typical night shift in women with regular menses 5.
- Prolactin levels can be measured at any time, but it is essential to consider the clinical presentation and medical history of the patient to ensure accurate interpretation of the results 2, 3.
Factors Affecting Prolactin Levels
- Various factors, such as pregnancy, lactation, and certain medications, can affect prolactin levels, and it is essential to consider these factors when interpreting prolactin level results 2, 3, 6.
- Prolactin levels can be affected by the time of day, and it is recommended to measure prolactin levels in the morning to ensure accurate results 2, 5.