Fatherhood and Testosterone: Why New Dads' Levels Fall, and Why That's Normal

Six months after his daughter was born, he went to his GP because he felt flat. Not miserable, just flat. His sex drive had faded, his gym sessions had shrunk to twice a week, and he was sleeping in four-hour pieces between night feeds.

A friend had told him to get his testosterone checked. It came back at the lower end of normal, well below where it had been in a work health check two years earlier. He left wondering whether something was wrong with him.

Probably not. One of the most consistent findings in men's hormone research is that testosterone falls when men become fathers, and the men who are most involved with their babies tend to show the biggest drop. It is a normal part of the transition, not a sign of decline. But it is worth understanding, because the same months that lower a new dad's testosterone also bring sleep loss, stress and a real risk of depression, and those need to be separated from the hormone itself.

The study that changed the picture

The key evidence comes from a long-running study in Cebu, in the Philippines. In 2011, Lee Gettler and colleagues published results from 624 men who had their testosterone measured at an average age of about 21 and a half, when none were fathers, and again around four and a half years later.

Two findings stood out.

First, men with higher testosterone at the start were more likely to have found a partner and become fathers by the second visit. Higher testosterone seems to support the business of finding a mate.

Second, once they became fathers, their testosterone fell sharply. New partnered fathers saw median declines of about 26% in their morning levels and 34% in their evening levels, far more than men who stayed single and childless. Fathers who reported three or more hours of childcare a day had lower testosterone than fathers who did none.

Because the same men were measured before and after, this was not simply a case of low-testosterone men being more likely to settle down. The order was the reverse: higher testosterone came first, and the fall followed fatherhood.

It starts before the baby arrives

A smaller study by Robin Edelstein and colleagues followed 29 couples expecting their first child. During the pregnancy, the expectant fathers' testosterone and oestradiol both fell, while cortisol and progesterone did not change. The hormonal shift seems to begin before the birth, not only once the sleepless nights start.

Closeness matters

Another Cebu study, of 362 fathers, looked at where they slept. Fathers who shared a bed or a room with their children had lower testosterone than fathers who slept apart, and larger drops as they became fathers. The more physically present a father is in the early years, the more his hormones seem to adjust.

Why would testosterone fall?

The leading explanation is a trade-off that runs right through human and animal biology. Testosterone supports effort spent on competing and finding partners. Caring for young takes a different kind of effort, and hormones shift to match.

In species where fathers help raise their young, males often show a similar fall in testosterone when offspring arrive. In species where they do not, they usually do not. Humans sit firmly in the first group, and the Cebu findings fit that pattern.

The fall is not an accident or a breakdown. It looks more like the body adjusting priorities.

Other things are going on at the same time

Not all of the change is purely about the baby. New fathers commonly:

• Sleep less and worse. Testosterone rises during sleep and peaks in the early morning, and a week of sleeping under five hours a night lowered daytime testosterone by 10 to 15% in one study of young men. See does sleep affect testosterone?
• Exercise less. The gym is often the first thing to go.
• Gain weight. Many men gain a few kilos during their partner's pregnancy and the first year. Extra body fat lowers testosterone.
• Feel more stressed. Long-term stress and raised cortisol can suppress the hormone. See does stress lower testosterone?

These are worth noticing, because unlike the fatherhood effect itself, they are things you can do something about.

Is lower testosterone a problem for new dads?

For most men, no. These studies describe a normal shift in healthy men, not a medical deficiency. A drop from the upper to the lower part of normal is not the same as a deficiency.

There may even be benefits. Lower testosterone has been linked in several studies to more responsive parenting and greater sensitivity to a baby's cues. The evidence is still developing, but the general picture is that the shift supports the job new fathers are being asked to do.

The depression link

This is where it gets more complicated. A 2017 study by Darby Saxbe and colleagues followed 149 couples after the birth of a child. Fathers with lower testosterone reported more depressive symptoms. But their partners reported fewer depressive symptoms, apparently because they were more satisfied with the relationship. Fathers with higher testosterone were more likely to show hostility towards their partners.

So the same hormonal shift that may help the family can leave some fathers more vulnerable to low mood. That matters, because depression in new fathers is common and under-recognised. A large meta-analysis by Paulson and Bazemore, covering 43 studies and more than 28,000 people, found that about one in ten fathers showed signs of depression during their partner's pregnancy or the first year after birth, with rates highest three to six months after the birth.

Paternal depression often looks different from the textbook picture. It may show up as irritability, working longer hours, drinking more, withdrawing from the family or losing interest in sex, rather than obvious sadness. We explore how to tell low mood and low testosterone apart in low testosterone and depression.

When to get checked

A testosterone test is reasonable if:

• symptoms such as very low libido, erectile problems, exhaustion or loss of muscle persist well beyond the newborn stage, once sleep has improved;
• you had symptoms before your partner's pregnancy;
• you have other risk factors, such as obesity, type 2 diabetes or sleep apnoea.

Testosterone should be measured in the morning, ideally between 7 and 11am, and a low result should always be repeated. A single test taken after a broken night with a newborn can easily mislead. See what blood test checks your testosterone and normal levels by age.

If the result is clearly low on repeat testing, your doctor should look for a cause rather than treat the number. And if you are thinking about more children, testosterone therapy is a poor choice, because it shuts down sperm production. See will TRT make you infertile?

What actually helps

You cannot, and probably should not, undo the fatherhood effect. But you can protect the parts of your health that new parenthood tends to wreck.

Protect sleep where you can

Sleep is the biggest lever. Take shifts with your partner so each of you gets one longer block of sleep a night, rather than both waking for every feed. Even one unbroken four- or five-hour stretch makes a real difference. Short daytime naps help too.

Keep some strength training

Two or three short sessions a week is enough to keep muscle and support your mood. A 25-minute home workout counts. See does lifting increase testosterone?

Watch the "sympathy weight"

Easy, high-calorie convenience food and less activity are why many new fathers gain weight. Keeping some structure to meals, with protein and vegetables, stops a small gain becoming a large one. Our recipes include quick, high-protein meals designed for exactly this.

Be honest about alcohol

A drink to unwind after the baby is asleep easily becomes a nightly habit. Alcohol worsens sleep quality and, in larger amounts, lowers testosterone. See the truth about alcohol and testosterone.

Talk about how you feel

If your mood has been low for more than two weeks, if you feel detached from your baby, or if you are struggling to cope, speak to your GP. Help for fathers is available, and the first year is exactly when it matters most. If you are ever thinking about harming yourself, contact NHS 111, your GP or Samaritans on 116 123 straight away.

The bottom line

Testosterone falling after you become a father is normal, well documented and probably useful. It is not a sign that you are ageing faster or losing your edge.

What deserves attention is everything that comes with it: broken sleep, less exercise, weight gain, stress and the real chance of postnatal depression. Look after those, and the hormones usually take care of themselves as your children grow.

Common questions

Does having a baby lower a man's testosterone?

Yes. In a study of 624 men followed over four and a half years, those who became fathers saw median falls of about 26% in morning and 34% in evening testosterone, much larger than men who did not.

Is it permanent?

It does not appear to be a permanent loss. Testosterone is responsive to sleep, stress, weight and activity, all of which change as children grow. There is no evidence that fatherhood alone causes testosterone deficiency.

Does testosterone drop during my partner's pregnancy?

It can. In a small study of 29 couples expecting their first child, the fathers' testosterone and oestradiol both fell during the pregnancy.

Should new fathers take testosterone?

Not because of fatherhood alone. A natural fall within the normal range is not a reason for treatment, and testosterone therapy stops sperm production, which matters if you want more children.

Can fathers get postnatal depression?

Yes. Around one in ten fathers show signs of depression during their partner's pregnancy or the first year after birth. It often shows up as irritability, withdrawal or drinking more, so speak to your GP if it sounds familiar.

Sources: Gettler LT et al., Longitudinal evidence that fatherhood decreases testosterone in human males, Proc Natl Acad Sci USA 2011;108(39):16194-9 · Edelstein RS et al., Prenatal hormones in first-time expectant parents: longitudinal changes and within-couple correlations, Am J Hum Biol 2015;27(3):317-25 · Gettler LT et al., Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines, PLoS One 2012;7(9):e41559 · Saxbe DE et al., High paternal testosterone may protect against postpartum depressive symptoms in fathers, but confer risk to mothers and children, Horm Behav 2017;95:103-12 · Paulson JF, Bazemore SD, Prenatal and postpartum depression in fathers and its association with maternal depression, JAMA 2010;303(19):1961-9 · Leproult R, Van Cauter E, Effect of 1 week of sleep restriction on testosterone levels in young healthy men, JAMA 2011;305(21):2173-4 · Educational only, not medical advice.

Keep reading: Low testosterone and depression · Does sleep affect testosterone? · Will TRT make you infertile? · Sperm count: what lowers it · Does stress lower testosterone? · Night shifts and testosterone