Oxytocin
Overview
Oxytocin measures a nonapeptide hormone synthesized in the hypothalamus and released from the posterior pituitary that mediates uterine contraction during labor and milk ejection during breastfeeding. It also functions as a neuromodulator influencing social bonding, trust, anxiety regulation, and pair bonding through central nervous system receptors. Clinical measurement primarily assesses deficiency states; elevated levels lack established diagnostic utility. Oxytocin testing remains largely investigational outside peripartum applications due to pulsatile secretion and assay challenges.
Clinical Use Cases
- Evaluating central diabetes insipidus (distinguishes from nephrogenic forms).
- Assessing pituitary function post-partum hemorrhage or pituitary surgery.
- Research applications in social behavior and psychiatric disorders.
- Investigating labor dystocia and breastfeeding difficulties.
Specimen Types
- Plasma (EDTA with aprotinin inhibitor).
- Serum (less stable).
Measurement Methods
- Radioimmunoassay (RIA).
- Enzyme immunoassay (ELISA).
- Liquid chromatography-mass spectrometry (research).
Test Preparation and Influencing Factors
- Supine position 30 minutes prior; avoid stress and nipple stimulation.
- Pulsatile secretion requires multiple sampling for accuracy.
- Exogenous oxytocin (Pitocin) massively elevates levels.
- Recent orgasm, exercise, or fasting transiently affect baseline.
Synonyms
- Oxyphysin.
- Posterior pituitary hormone.