Aligning hormone treatment administration with the body’s natural circadian rhythms could enhance efficacy, reduce adverse effects, and even cut down on the need for multiple daily doses, emerging research suggested.

“Since many hormones follow a circadian rhythm, administering them at inappropriate times may result in suboptimal efficacy or increased adverse effects,” Mikiko Watanabe, MD, of Sapienza University of Rome, Rome, Italy, told Medscape Medical News. “Studying the timing allows us to better align therapies with the body’s physiological rhythms, improving clinical outcomes while reducing risks.”

Chronotherapy: Taking Advantage of the ‘Master Clock’

Chronotherapy — timing drug administration to match circadian biology — draws on the close ties between the endocrine and nervous systems.

In a recent Endocrine Reviews article, Watanabe and colleagues explained how chronotherapy takes advantage of the connections between the endocrine and nervous systems. The bilateral suprachiasmatic nuclei (SCN) — the body’s “master clock” — regulate endocrine activity and other biologic functions on an approximately 24-hour cycle. This rhythmic gene expression extends beyond the SCN to “peripheral clocks” in most cells and tissues, driving processes including sleep-wake cycles, feeding-fasting, and physical activity.

Because these fluctuations influence pharmacokinetics (absorption, distribution, metabolism, and excretion) and pharmacodynamics (drug activity and duration), “the timing of drug administration could therefore play an important role in determining key pharmacokinetic parameters,” Watanabe and colleagues wrote.

Timing Matters: Thyroid and Glucocorticoid Treatments

Chronotherapy is particularly relevant for glucocorticoid therapy.

“When administered in the early morning, hydrocortisone supports the physiological circadian rise in cortisol, benefiting patients with adrenal insufficiency,” Watanabe said. “By contrast, when administered at night, certain formulations such as modified-release hydrocortisone are able to suppress the early-morning adrenocorticotropic hormone surge required in congenital adrenal hyperplasia.”

Tailoring timing to circadian physiology allows physicians to achieve different therapeutic goals, she told Medscape Medical News, as evidenced with thyroid hormones.

Levothyroxine is typically taken in the morning on an empty stomach, but studies have shown that bedtime administration may be equally effective — and sometimes better tolerated — if meals and bedtime are sufficiently spaced. This approach can help patients struggling with morning routines or adherence, though Watanabe cautioned that food and drug interactions must still be considered.

Treatment plans based on chronotherapy should consider individual sleep-wake cycles and chronotype (natural tendencies toward morning or evening) to optimize both therapeutic consistency and patient satisfaction, Watanabe said. However, evidence on optimal timing for thyroid-stimulating hormone and thyroxine remains limited and sometimes conflicting.

Evidence Varies Across Therapies

For some therapies, such as long-acting insulin, clinical evidence for chronotherapy is still emerging. Current research also hasn’t shown any advantage to timing contraceptives, although it is recommended to consistently take these medications at the same time each day.

“Given the extreme complexity and variability of both estrogen and progesterone circadian and ultradian rhythms, it is unlikely that any specific administration timing may prove better than others,” Watanabe and colleagues wrote in their review.

More data exist on the association between circadian rhythms and glucocorticoids. One small study in the Journal of Clinical Endocrinology & Metabolism showed that transitioning adults with Cushing syndrome from a twice-daily osilodrostat dose to a single daily dose at 19:00 (7:00 PM) significantly improved both sleep and quality of life without compromising safety or disease control.

In congenital adrenal hyperplasia, a bedtime dose of delayed-release hydrocortisone has been shown to better mimic the body’s natural cortisol cycles, improve disease control, and reduce overall steroid use.

Tune In to Time Tracking

A 2020 Clinical Pharmacology & Therapeutics review called for clinicians to track the time of day patients take medications as a key biologic variable in studies.

Tracking the effect of timing on hormone therapy is important because many hormones are secreted in a rhythmic fashion and can have very different effects at different times of day, said Amita Sehgal, PhD, a molecular biologist and chronobiologist at the Perelman School of Medicine at the University of Pennsylvania, Philadelphia.

Sehgal coauthored a 2021 review that cited studies in which the body’s circadian clocks served as drug modulators in treating a range of diseases including nervous system conditions such as epilepsy, hypertension, autoimmune disease, and cancer.

Sehgal told Medscape Medical News that since the review’s publication, the field has shifted further to recognize that even therapies with long-term effects (days or weeks) can be influenced by the timing of their delivery on the basis of the circadian regulation of their targets.

Sehgal sees no downsides to incorporating chronotherapy in endocrinology, provided that patients’ endogenous rhythms are taken into account. Standardized protocols for time-specific blood sampling and outcome monitoring could help ensure that circadian-informed strategies are more widely adopted in practice, Watanabe added.

Ultimately, identifying how chronotype influences drug metabolism and efficacy could pave the way for more personalized therapies and improve adherence.

Research Gaps and Next Steps

Chronotherapy, while promising, faces several limitations, Watanabe told Medscape Medical News.

“The circadian profile of hormone secretion may vary significantly between individuals and is influenced by age, comorbidities, sleep hygiene, or lifestyle,” she said. “The evidence base for the optimal timing of many hormone therapies is still incomplete, and most current guidelines do not provide specific recommendations.”

Practical challenges include the use of long-acting medications that limit precise timing and patient compliance issues with time-targeted regimens.

Future research should include prospective, controlled trials assessing both short-term outcomes and long-term safety.

“The role of chronotype — an individual’s intrinsic preference for activity and alertness at certain times of day — should be more systematically incorporated into treatment planning,” Watanabe added.

The Endocrine Reviews article reported receiving no outside funding, and the researchers had no financial conflicts to disclose. Sehgal had no financial conflicts to disclose.