How winter's hormonal shifts and low sunlight affect reproductive health

Fewer daylight hours and winter stress can disrupt hormonal signalling, affecting fertility in both men and women. Specialists explain the seasonal effects and how to manage them

As winter sets in, most people notice changes in energy, mood, and sleep. What often goes unnoticed is that the same seasonal shift can quietly influence reproductive hormones in both women and men. Shorter daylight hours, reduced sun exposure, and altered routines may not dramatically change fertility overnight, but experts say they can subtly affect cycles, sperm health and libido, especially in those already dealing with hormonal imbalances.

 

Doctors emphasise that winter-related changes are usually mild and reversible. Understanding what is happening inside the body can help people take timely steps to protect reproductive health.

 

The daylight–hormone connection

 

One of the biggest biological changes during winter is reduced exposure to sunlight. According to Dr Puneet Rana Arora, Gynecologist and IVF Expert at CIFAR, Gurugram, shorter days increase the secretion of melatonin, the hormone that regulates sleep.

 

“The shorter period of daylight leads to the secretion of melatonin, which will inhibit the hypothalamic-pituitary-gonadal axis,” Dr Arora explains. This hormonal system regulates the release of oestrogen, progesterone and testosterone. When it is suppressed, ovulation may be delayed, sperm production can dip slightly and libido may reduce, particularly in people with underlying hormonal sensitivity.

 

Winter also disrupts sleep and daily routines, adding another layer of hormonal stress. “Winter stress, lack of sleep, and circadian rhythm disturbances increase cortisol levels,” Dr Arora says. Higher cortisol can suppress the hormones that stimulate the ovaries and testes, leading to lower reproductive hormone levels and symptoms such as cycle irregularity, reduced sperm quality, fatigue and low mood.

 

Dr Priyanka Yadav, Fertility Specialist at Birla Fertility & IVF, Jaipur, notes that circadian rhythms play a far bigger role in reproductive health than most people realise. When sleep and routines become irregular, hormonal balance and sexual drive can suffer.

 

Vitamin D deficiency and fertility signals

 

Another winter-linked concern is vitamin D deficiency. With people spending more time indoors and covering up outdoors, levels often drop without obvious symptoms.

 

“There are vitamin D receptors in the ovaries, uterus, testes and even sperm,” says Dr Arora. Low levels have been associated with irregular menstrual cycles, ovulatory disorders, worsening of polycystic ovary syndrome (PCOS), and poorer sperm motility and morphology.

 

Dr Yadav adds that the impact is rarely dramatic but can matter when conception is already taking time. “Vitamin D plays an important role in ovarian function, endometrial health and sperm movement. When it’s low, cycles can become unpredictable and sperm parameters may quietly dip,” she says.

 

The good news, both experts note, is that these effects are usually mild and reversible once vitamin D levels are corrected.

 

Why cycles and PMS can feel worse in winter

 

Many women report that their cycles feel “off” during winter, as periods may be delayed by a few days, PMS symptoms feel heavier, and fatigue is more pronounced. Dr Arora says this can be traced to a combination of factors:

 

• Changes in melatonin and cortisol levels
• Reduced physical activity
• Lower vitamin D
• Disrupted circadian rhythms

 

These shifts can influence oestrogen and progesterone secretion, as well as neurotransmitters involved in mood and pain perception. Dr Yadav notes that seasonal changes in serotonin, the brain chemical linked to mood, may also explain why PMS symptoms feel more intense during colder months.

 

Seasonal effects on men’s reproductive health

 

Men are not immune to winter-related changes. Experts say there is mild seasonal suppression of testosterone during colder, darker months, linked to lower sunlight exposure, vitamin D deficiency and reduced activity.

 

“There are also seasonal variations in sperm count and motility,” Dr Arora says, “though these are often less significant than lifestyle and metabolic factors such as weight, diet and smoking.”

 

Dr Yadav echoes this view, noting that stress, poor sleep and inactivity can amplify seasonal dips in sperm quality.

 

Simple tips to stabilise hormones in winter

 

Both experts stress that winter does not “cause infertility,” but it can magnify existing vulnerabilities. Simple, consistent habits can help buffer the seasonal effects:

 

• Maximise exposure to morning sunlight
• Maintain adequate vitamin D levels
• Stay physically active
• Eat a balanced, wholesome diet
• Prioritise sleep and stress management
• Avoid smoking, excessive alcohol and weight gain

 

“For couples trying to conceive, winter is a good time to check for deficiencies and hormonal imbalances that can be corrected,” Dr Arora advises.

 

Dr Yadav notes that winter changes how the body behaves hormonally, but small lifestyle adjustments can go a long way in keeping reproductive health on track through the season.   

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This report is for informational purposes only and is not a substitute for professional medical advice.