Serum prolactin bioactivity and immunoactivity in hyperprolactinaemic states

Area of Science:

• Endocrinology
• Molecular Biology
• Clinical Chemistry

Background:

• Prolactin is a key hormone regulating numerous physiological processes.
• Elevated prolactin levels (hyperprolactinaemia) can indicate pituitary tumors (prolactinomas) or physiological states like postpartum lactation.
• Accurate measurement of prolactin is crucial for diagnosis and monitoring.

Purpose of the Study:

• To investigate the bioactivity versus immunoactivity of serum prolactin in patients with prolactinomas and in lactating women.
• To determine if molecular heterogeneity of prolactin differs between pathological and physiological hyperprolactinaemia.
• To assess the correlation between prolactin bioactivity:immunoactivity ratio and serum prolactin levels.

Main Methods:

• Serum prolactin concentrations were measured using a sensitive Nb2 bioassay and radioimmunoassay.
• Measurements were performed in 11 patients with prolactinomas and 58 normal controls.
• Ten lactating women in the early postpartum period were studied as a model of physiological hyperprolactinaemia.

Main Results:

• Patients with prolactinomas exhibited significantly lower serum prolactin bioactivity to immunoactivity ratios compared to controls.
• Lactating women also showed reduced bioactivity to immunoactivity ratios.
• A significant negative correlation was observed between the bioactivity:immunoactivity ratio and serum immunoactive prolactin levels.

Conclusions:

• Altered relative bioactivity of prolactin in hyperprolactinaemic states suggests changes in its molecular heterogeneity.
• These molecular changes may influence the accuracy of both bioassays and radioimmunoassays for prolactin.
• Further research into prolactin isoforms is warranted for improved diagnostic and therapeutic strategies.