Published Apr 15, 2026 | 7:29 AM ⚊ Updated Apr 15, 2026 | 7:29 AM
Night shift workers were younger on average, at 28.6 years against 31.1 years among day workers, and carried lower body mass index scores.
Synopsis: A study by researchers at Gandhi Medical College in Hyderabad finds that night shift workers at a multinational company show disrupted hormonal patterns and poorer metabolic health, leading to reduced fertility. The research indicates that irregular sleep cycles disturb the brain’s hormonal regulation, leading to lower testosterone in men and altered reproductive hormones in women, alongside higher rates of insulin resistance and related risks.
Night shift workers at a multinational company in south India show lower testosterone, disrupted luteinising hormone and higher oestradiol than day shift workers, according to a study by researchers at Gandhi Medical College, Hyderabad, raising concerns about the impact of irregular schedules on fertility.
The findings land at a time when India’s night shift workforce continues to expand across IT, healthcare, and manufacturing, with millions of workers in their twenties and thirties spending their most reproductively active years working through the night.
The cross-sectional study, conducted between March 2020 and March 2022, compared 45 night shift workers with 45 day shift workers from the same multinational company in South India. Researchers measured metabolic and hormonal markers across both groups.
Night shift workers were younger on average, at 28.6 years against 31.1 years among day workers, and carried lower body mass index scores. Despite this, they showed worse health outcomes across nearly every marker the researchers measured.
77 percent of night shift workers showed insulin resistance, a precursor to type 2 diabetes, against 62 percent among day workers. Triglyceride levels ran higher at 195 mg/dl against 180 mg/dl. HDL, or good cholesterol, ran lower at 35 mg/dl against 40 mg/dl.
But it is the hormonal findings that raise the fertility question most directly.
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Dr Pratibha Tiwary, consultant fertility specialist at Oasis Fertility, Hyderabad, says the metabolic findings alone carry fertility implications before the hormonal disruption even enters the picture.
“Fertility is a reflection of your overall health. If there is an increase in metabolic diseases such as hypertension and diabetes, it will certainly affect fertility as well,” she told South First.
The study’s findings on insulin resistance and lipid profiles therefore matter not just for cardiovascular risk but as upstream signals of reproductive stress.
Dr Tiwary explains that the damage begins in the brain.
“Night shift workers have a disrupted sleep-wake cycle. They are working and experiencing stress at a time when they should actually be sleeping. The brain remains active when it should be resting,” she said.
The part of the brain that coordinates hormones and the sleep cycle, primarily the hypothalamus, takes the first hit.
“The brain regulates multiple hormonal systems through the hypothalamic-pituitary-gonadal axis. The pulsatile release of hormones from the brain coordinates with the pancreas and, in turn, affects the gonadal axis. By gonads, I mean the ovaries in females and the testes in males,” Dr Tiwary said.
This axis governs reproductive function in both men and women. When circadian disruption breaks the timing and quantity of hormonal pulses, the consequences travel down into the reproductive system.
“The hypothalamic-pituitary axis is the main element that governs both sleep patterns and reproductive hormones. If one is disturbed, the other will also be affected,” she said.
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Male night shift workers in the Gandhi Medical College study recorded luteinising hormone levels of 2.8 mIU/ml against 5.6 mIU/ml among day shift men, and testosterone levels of 373.6 ng/dl against 400 ng/dl.
“Hormones such as LH and FSH, which are secreted from the brain, depend on precise timing and quantity in each cycle. When this pulsatility is disturbed, testosterone levels decrease. This leads to changes in semen parameters, including sperm count and motility,” Dr Tiwary said.
She places the testosterone finding from the study in clinical context.
“Typically, a range of around 350 to 800 nanograms per deciliter is considered normal. In males, testosterone is the primary hormone that drives libido and fertility. Lower levels can affect libido and may lead to issues such as erectile dysfunction, ejaculatory dysfunction, and premature ejaculation,” she said.
The study authors note that previous research found low testosterone in male shift workers and linked it to higher risk of erectile dysfunction, a finding that aligns with their own results.
Female night shift workers in the study showed oestradiol levels of 181 pg/ml against 100 pg/ml among day shift women, nearly double the levels recorded in the day shift group.
Dr Tiwary explains why this matters for ovulation.
“In females, the system is even more sensitive because it follows a cyclical pattern. Every month there is a menstrual cycle. If LH and FSH are disturbed, ovulation is affected. The formation and release of an egg in each cycle can be disrupted,” she said.
On FSH specifically, she adds that the hormone’s natural variation across the menstrual cycle is itself critical.
“The pulsatile release and appropriate quantity of FSH are essential for follicle development. Persistently low, stagnant, or excessively high levels of FSH are not favourable for fertility,” Dr Tiwary said.
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The study found that 22 percent of night shift workers showed subclinical hypothyroidism against 11 percent among day workers. Vitamin D levels also ran significantly lower in the night shift group at 10.4 ng/ml against 13.7 ng/ml, which the study authors attribute to reduced sunlight exposure.
Dr Tiwary says both findings carry direct reproductive consequences.
“Vitamin D plays a significant role across multiple aspects of health, including fertility. It has been linked to several gynaecological conditions such as PCOD, endometriosis, and fibroids. Receptors for vitamin D are present in various parts of the reproductive system, including the gonads and the uterus,” she said.
“Maintaining adequate vitamin D levels is important, and it is routinely assessed as part of fertility evaluation. This helps ensure that both egg and sperm quality are optimal,” Dr Tiwary added.
The authors of the Gandhi Medical College study describe this accumulation of disruptions as a paradox, where circadian rhythm disruption rather than obesity drives the metabolic and hormonal damage.
“The novelty of our findings lies in demonstrating that even with lower BMI and waist circumference, night-shift workers have significant metabolic and endocrine derangements. This underscores that body weight alone may underestimate cardiometabolic risk in this group,” they said.
Dr Tiwary draws a distinction between short-term and long-term exposure.
“There is always a difference between acute and chronic exposure to any high-risk factor. Going for a night job or working night shifts for a limited period is not something I would say will affect long-term health. However, how it is compensated, and how the work-rest cycle is coordinated, will definitely have an impact,” she said.
Recovery from prolonged night shift work takes time.
“I have read that even for one night of disturbed sleep, you may need at least two to three days of good sleep to compensate. Putting a fixed time frame on recovery is difficult. However, such workers will definitely need a well-planned compensatory model,” Dr Tiwary said.
Dr Tiwary says that occupational history already forms part of fertility assessment in her practice, but awareness needs to travel further.
“Detailed history-taking regarding the type of work the couple is doing is already a part of our assessment. We also inquire about the psychological aspects of their work. There is already a certain level of anxiety and depression in couples, and the psychological aspect, along with their occupation, is an important part of history-taking,” she said.
The Gandhi Medical College study authors call for screening programmes that move beyond weight and waist measurements.
“Screening and intervention strategies for shift workers must therefore go beyond anthropometric measures and address circadian and hormonal pathways,” they said.
With India’s night shift workforce concentrated in its most reproductively active age group, the study and the specialists who read it arrive at the same conclusion: the cost of working through the night extends well beyond fatigue, and it shows up in the very hormones that determine whether a person can have a child.
