Diurnal Variation
Pronunciation: die-UR-nal
Predictable daily fluctuations in hormone levels that affect optimal testing times and result interpretation.
Full Definition
Diurnal variation refers to the normal cyclical changes in hormone concentrations throughout a 24-hour period, driven by circadian rhythm and physiological demands. Cortisol, testosterone, growth hormone, and thyroid-stimulating hormone all exhibit significant diurnal patterns. Understanding these patterns is crucial for proper test timing and accurate interpretation of results. For example, cortisol peaks in the early morning and reaches its lowest levels around midnight, while growth hormone typically surges during deep sleep. Clinical editors must ensure that collection times are documented and that reference intervals appropriate for the collection time are used.
Usage
Usage note: Specify collection time when documenting results of hormones with diurnal variation.
In Context
- "The cortisol result must be interpreted considering normal diurnal variation patterns." — Laboratory interpretation note
- "Diurnal variation in testosterone requires morning collection for accurate assessment." — Hormone testing protocol