rolactin (PRL) is a peptide secreted II by acidophilic pituitary lactomorph I cells under the dual control of a dopaminergic prolactin inhibiting factor (PIF) and serotonergic prolactin releasing factor (PRF). Thyrotropin releasing factor (TRF) promotes the release of PRL and thryrotopin (TSH), whereas estrogen releases PRL via direct stimulation of the pituitary (1).
Normal adults exhibit little change in serum PRL during waking hours, except for brief elevations after naps (2). Multiple nocturnal PRL surges occur which, unlike growth hormone (GH), are not entrained to specific sleep stages (3). Serum PRL returns to daytime values within 90 minutes of waking.
The neonatal state is associated with high levels of serum PRL. Other physiologic elevations of PRL occur during pregnancy, preparatory to lactation, and during lactation itself. Breast manipulation during nursing or sexual activity produces a transient increase in serum PRL (Table 5.1).
Was this article helpful?