Measurement of changes in the serum prolactin concentration can be used as supportive evidence for the diagnosis of an epileptic seizure.


The rise in prolactin is seen after generalized tonic-clonic or partial complex seizures. The peak level is seen 15-20 minutes after the event. The half-life of the prolactin is about 20 minutes, and there is a return to pre-ictal levels after 60 minutes.


Sample collection should be standardized for optimum usability:

(1) Ideally this would be 20-30 minutes after the episode. A sample more than 60 minutes after the seizure will likely be a false negative.

(2) Baseline level, either drawn more than 60 minutes after the seizure or on a day without seizure activity.


Criteria for elevations in serum prolactin seen in epileptic seizures:

(1) A level 2 times baseline levels (some use 3 times baseline).

(2) A level more than 3 standard deviations above the baseline.


Serum prolactin levels can help distinguish pseudoseizures from true seizures. However, this may be limited:

(1) by the prevalence of pseudoseizures in the population (see Table 2, page 1225, Yerby et al, 1987).

(2) in patients with concurrent epilepsy and pseudoseizures


The absence of a rise in prolactin does not exclude the diagnosis of epilepsy. Prolactin levels will not be elevated if (Sperling et al):

(1) the seizure was brief (< 10 seconds), or

(2) there was no loss of consciousness.

A sample drawn more than 60 minutes after the event will miss an elevated value.


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