On the nature of serum prolactin in two patients with macroprolactinemia

Fertil Steril. 1992 Jul;58(1):78-87.


Objective: To further characterize the high molecular weight (MW) forms of prolactin (PRL) present in patients with macroprolactinemia.

Design: Case reports with laboratory investigations.

Setting: Academic medical centers.

Patients: Two patients with macroprolactinemia.

Interventions: Measurements of PRL concentrations before and after chromatographic separations.

Results: The majority of serum PRL had an estimated MW of at least 669 kd in the first patient and approximately 171 kd in the second. During a pregnancy, a new form of PRL (MW 291 kd) appeared in the first patient's serum and persisted for at least 3 years. Immunoprecipitation and polyacrylamide gel electrophoresis under reducing and denaturing conditions revealed that the largest form of PRL (MW 669 kd) was composed mostly of 25 kd glycosylated PRL; intermediate forms (171 kd and 291 kd) were composed of roughly equal portions of 25 kd glycosylated PRL and 23 kd nonglycosylated PRL, whereas "little" PRL in these patients was composed primarily of 23 kd nonglycosylated PRL. Injection of the first patient's serum into rats demonstrated that the human PRL (hPRL) immunoreactivity was cleared from the serum more slowly than the PRL from sera containing predominantly little hPRL; after stimulation with thyrotropin-releasing hormone in the second patient, serum PRL concentrations decayed more slowly than observed in normal subjects.

Conclusions: Large forms of serum PRL are at least partially glycosylated. These large forms are heterogeneous, both within and among patients. Delayed clearance may account for increased serum PRL concentrations in patients with macroprolactinemia.

Publication types

  • Case Reports
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Chromatography, Gel
  • Female
  • Humans
  • Hyperprolactinemia / blood*
  • Immunoassay
  • Molecular Weight
  • Precipitin Tests
  • Pregnancy / blood
  • Prolactin / analysis
  • Prolactin / blood*
  • Prolactin / chemistry


  • Prolactin