How jet lag disrupts your thyroid
- 4 days ago
- 5 min read
Jet lag isn’t just about sleep
Most people think of jet lag as a temporary inconvenience such as fatigue, poor sleep, maybe some brain-fog. However, jet lag has a holistic impact on several hormonal systems. Most importantly your thyroid and prolactin are disrupted for weeks after you land in the "new time-zone".
Especially neurodivergent people, or menopausal women, whom may already be dealing with burnout or hormonal sensitivity may struggle with the impacts for weeks after feeling "normal".
Your circadian rhythm controls more than you think
Your body runs on a central “clock” located in the brain, which regulates daily rhythms in:
Sleep and wake cycles
Hormone release
Metabolism
Body temperature
This system also tightly regulates the hypothalamic–pituitary–thyroid (HPT) axis, which controls thyroid hormone production.
The hypothalamus releases TRH
TRH stimulates TSH from the pituitary
TSH stimulates thyroid hormone (T4 → T3) production
T3 feeds back to regulate the system
This loop is not static—it is circadian-controlled, meaning timing matters and disruption to daily patterns may have an acute impact.
Sleep, circadian rhythm, and your thyroid
Here’s where things get interesting. Research shows that:
TSH follows a circadian rhythm, typically rising overnight
When we sleep, we suppress/control TSH release
When sleep is disrupted, this balance shifts
In fact, after a single night of sleep deprivation, TSH levels can be roughly doubled the next morning.
This means that your thyroid markers can change significantly based on sleep alone. Blood tests taken after travel may not reflect your true baseline.
Important to note is: repeated or chronic circadian disruption is associated with increased risk of:
Obesity
Diabetes
Cardiovascular disease
Thyroid dysfunction
How jet lag impacts your hormones
When you cross time zones, your internal clock doesn’t instantly reset. Instead, your body continues operating on the time where you spent the last week or so — while your environment has shifted. This leads to:
Misaligned hormone secretion
Hormones are released at the “wrong” time relative to your environment.
Sleep disruption
Which further amplifies hormonal dysregulation.
Temporary endocrine chaos
Particularly affecting thyroid and prolactin pathways.
Prolactin, the overlooked hormone
Prolactin (PRL) is often thought of as a “lactation hormone,” but it plays a much broader role:
Immune regulation
Reproductive hormone balance
Stress response
Metabolic signalling
It also follows a strong circadian rhythm, with peak levels occurring overnight—particularly during REM sleep.
Studies show that after long-haul travel:
Prolactin rhythms become misaligned
“Anamnestic peaks” (old time-zone patterns) can persist
Full normalisation can take 11–21 days after travel
In other words, your body can remain hormonally “out of sync” for weeks after a trip
Even when your sleep feels normal again.
Thyroid and prolactin are connected
The connection between prolactin and the thyroid are often overlooked. TRH (thyrotropin-releasing hormone) doesn’t just stimulate TSH—it also stimulates prolactin.
So when thyroid signalling changes, prolactin often shifts too.
In hypothyroidism, for example:
Elevated TRH can increase prolactin
Up to 30–40% of patients with hypothyroidism may have elevated prolactin
This can impact reproductive hormones and mood
There is also evidence of a bidirectional relationship:
Thyroid dysfunction can alter prolactin
Prolactin may influence immune pathways and autoimmunity
Why this matters
Hormonal disruption from insomnia can contribute to:
Mood instability
Increased anxiety
Cognitive fog
Sleep fragmentation
Cycle irregularities
Increased sensitivity to stress
For women in perimenopause or menopause:
Prolactin changes can influence oestrogen signalling
HRT responses may feel inconsistent
Sleep disruption becomes more pronounced
For neurodivergent individuals:
Circadian dysregulation is often already present
Additional disruption can feel disproportionately intense
Timing of blood tests matters
It is really important that patients having thyroid tests must wait 4 weeks after after travel or extended poor sleeping patterns.
Given what we know:
TSH can be elevated after sleep deprivation
Hormone rhythms can remain altered for weeks post-travel
This can lead to misrepresentation of thyroid function. If possible:
Avoid testing immediately after long-haul travel
Ensure consistent sleep for several days prior
Always test your thyroid at the same time of day each time, fasting.
My advice in clinic it always do your blood tests first thing in the morning, before having anything to eat or drink other than water.
Always use the same pathology lab, so the results can be compared without inconsistencies in laboratory equipment.
Supporting your body through jet lag
Rather than just “pushing through,” we want to help your body to regain its rhythm.
1. Light exposure is everything
Morning light → helps reset circadian clock
Avoid bright light late at night
2. Anchor your sleep-wake timing
Wake up at the same time daily
Even if sleep was poor
3. Support metabolic cues
Eat at local times (even if not hungry initially)
Prioritise protein early in the day
4. Be cautious with medications
Certain medications such as doxylamine, which are sometimes used to reset sleep can:
Influence histamine pathways
Potentially affect prolactin regulation
5. Give your body time
Summary
Full hormonal realignment can take: Up to 2–3 weeks. Even if you feel “mostly fine.”
Jet lag is not just a sleep issue. It is a temporary endocrine disruption involving:
Circadian rhythm
Thyroid function
Prolactin signalling
For many people—especially those already hormonally or neurologically sensitive—it can have a meaningful impact on how they feel. Understanding this allows you to:
Be more compassionate with yourself and your body
Interpret symptoms more accurately
Avoid unnecessary interventions or misdiagnosis
Sources:
Ikegami K, Refetoff S, Van Cauter E, Yoshimura T. Interconnection between circadian clocks and thyroid function. Nat Rev Endocrinol. 2019 Oct;15(10):590-600. doi: 10.1038/s41574-019-0237-z. Epub 2019 Aug 12. PMID: 31406343; PMCID: PMC7288350.
Bahar A, Akha O, Kashi Z, Vesgari Z. Hyperprolactinemia in association with subclinical hypothyroidism. Caspian J Intern Med. 2011 Spring;2(2):229-33. PMID: 24024022; PMCID: PMC3766941.
Melmed S, Casanueva FF, Hoffman AR, Kleinberg DL, Montori VM, Schlechte JA, et al. Diagnosis and treatment of hyperprolactinemia: an endocrine society clinical practice guideline. J Clin Endocrinol Metabolism. 2011;96(2):273–88.
Gungoren MS, Topcu DI, Zungun C. The effect of jet-lag on serum concentrations of thyroid stimulating hormone and prolactin: A case report. Biochem Med (Zagreb). 2020 Feb 15;30(1):011003. doi: 10.11613/BM.2020.011003. PMID: 32063733; PMCID: PMC6999183.
DANIEL DESIR, EVE VAN CAUTER, MARC L'HERMITE, SAMUEL REFETOFF, CLAUDE JADOT, ANNE CAUFRIEZ, GEORGES COPINSCHI, CLAUDE ROBYN, Effects of “Jet Lag” on Hormonal Patterns. III. Demonstration of an Intrinsic Circadian Rhythmicity in Plasma Prolactin, The Journal of Clinical Endocrinology & Metabolism, Volume 55, Issue 5, 1 November 1982, Pages 849–857, https://doi.org/10.1210/jcem-55-5-849
Pałubska S, Adamiak-Godlewska A, Winkler I, Romanek-Piva K, Rechberger T, Gogacz M. Hyperprolactinaemia - a problem in patients from the reproductive period to the menopause. Prz Menopauzalny. 2017 Mar;16(1):1-7. doi: 10.5114/pm.2017.67364. Epub 2017 Apr 26. PMID: 28546800; PMCID: PMC5437053.
Tahir Omer & Adnan Adnan, Hyperprolactinaemia in postmenopausal women receiving long-term hormone replacement therapy: a case series -
Endocrine Abstracts (2022) 81 EP931 | DOI: 10.1530/endoabs.81.EP931
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