Intermediate
Technical
In the Industry Vocabulary Test
Circadian Rhythm
Pronunciation: sir-KAY-dee-an
The 24-hour cycle affecting hormone production and release patterns.
Full Definition
Circadian rhythms are endogenous biological cycles that regulate hormone secretion over approximately 24-hour periods. Many hormones, including cortisol, growth hormone, and melatonin, exhibit distinct circadian patterns that must be considered when timing blood collection for accurate interpretation. Disruption of these rhythms through shift work, travel, or disease can significantly affect hormone test results and clinical assessment.
Usage
Usage note: Use 'circadian' not 'circa-dian' or 'circa dian'.
In Context
- "Cortisol follows a circadian rhythm with peak levels in the early morning." — Laboratory collection protocol
- "Growth hormone testing should account for circadian rhythm variations." — Pediatric endocrinology guideline
Also known as
Diurnal rhythm
Biological clock
Daily rhythm
Don't confuse with
Ultradian rhythm
Infradian rhythm
Seasonal rhythm