Prolactin reference range and pulsatility in male dogs.

Little is known about serum prolactin (PRL) concentrations and secretion patterns in male dogs. Blood samples (n = 65) were collected from crossbred dogs and from Beagles and German Shepherd dogs to describe the PRL reference range, and from five male Beagles at 15-min intervals for 6 h (n = 24 samples/dog) to describe the ultradian rhythm of this hormone. Serum PRL was measured by a homologous endpoint enzyme immunometric assay.