Sleep is where your hormones (& health) are made

Most people think of sleep as time off. It is closer to a night shift. While you sleep, your body releases growth hormone, builds testosterone, winds cortisol down, and resets the signals that run blood sugar and hunger. 1 2 3 4 When that shift is cut short or broken up, the whole next day runs on less.

We hear two sleep stories over and over. In the first, falling asleep is easy, and then it is 3am and the brain is wide awake. In the second, the tracker says eight hours and a decent score, and the morning still feels like being hit by a truck. Both deserve more than “try to relax.” Both deserve an investigation.

The night shift

Growth hormone. The biggest, most reliable growth hormone pulse of the day arrives shortly after you fall asleep, in the first stretch of deep sleep. Push bedtime later and the pulse moves with it. 1 5 In a study of 149 men, deep sleep fell from about 19% of the night in the late teens and early twenties to about 3% by midlife, and growth hormone fell right along with it. 6

Testosterone. Testosterone rises while you sleep and falls while you are awake. In studies of young men, the rise followed sleep, not the clock: men who slept during the day got the same climb as men who slept at night. It starts at sleep onset and peaks around the first stretch of dream sleep. 7 2 In a small study, broken sleep that kept cutting dream sleep short delayed or blunted the rise. 8 9

Cortisol. Cortisol is supposed to be low at night and to rise before you wake. In lab studies of young adults, short or broken sleep pushed it the wrong way: higher in the evening and slower to wind down. 3 10

Blood sugar and hunger. A week of short sleep made healthy young men less sensitive to insulin, 11 and in a smaller study, four short nights reached all the way to their fat cells. 12 Short sleep also shifts hunger signals, and people eat more. Pooled trials found about 385 extra calories a day, with no extra calories burned. 13 4

Melatonin. Melatonin rises with darkness and tells your body it is night. Light is the switch. 14

The brain’s cleaning crew. This is one of the most exciting open questions in sleep science. In mice, sleep seemed to open space in the brain and speed the clearance of waste, including amyloid. 15 Then a 2024 mouse study found clearance slowed during sleep, and researchers are still arguing about it. 16 In people, early studies found that deep-sleep brain waves move in step with pulses of spinal fluid, and that one sleepless night slowed a tracer leaving the brain. 17 18 Early science, and worth watching.

What breaks the night shift

Light at the wrong time. Light is a hormone signal. Ordinary room light in the evening delays melatonin and shortens your biological night by about 90 minutes. 14 Some people are far more sensitive to evening light than others. 19 In one laboratory study, a single night sleeping with a moderate light on raised next-morning insulin resistance. 20 In UK adults over 40 who wore light sensors, brighter nights were linked with higher later rates of diabetes, heart disease, and death, and brighter days were linked with living longer. 21 22 23

An irregular schedule. In a study of about 61,000 adults, sleep regularity predicted the risk of death more strongly than sleep duration did. 24 In a second UK study of about 72,000 adults, irregular sleep was linked with more heart attacks, strokes, and heart failure, and enough hours did not cancel that out for the most irregular sleepers. 25 Weekend catch-up sleep may help a little, but in a controlled trial it did not prevent the insulin and eating effects of short weeknights. 26 27

The nightcap and the afternoon coffee. Alcohol can make it easier to fall asleep and harder to stay asleep. 28 Your wearable is not lying about the nightcap: overnight recovery, measured as heart-rate variability, dropped with alcohol in a dose-dependent way, even at low intake. 29 Across studies, caffeine cost about 45 minutes of sleep, and a regular cup of coffee needed about nine hours before bed to avoid that loss. 30

Stress. Cortisol, the body’s main stress hormone, comes from the adrenal glands, and stress and sleep push on each other. 3 10 When sleep falls apart, I look at stress, adrenals included. Plenty of people online blame every 3am wake-up on a cortisol spike. Stress is one suspect. So are alcohol, apnea, night sweats, and a full bladder. 28 31

Heat. A hot bedroom hurts sleep. In older adults sleeping at home, sleep was best between about 68 and 77 °F, and sleep efficiency dropped 5% to 10% as rooms warmed toward 86 °F. 32 Cool, not cold.

Sleep apnea, the hidden one. Obstructive sleep apnea means breathing repeatedly narrows or stops during sleep. It is very common, and much of it goes undiagnosed. 33 34 It does not always sound like loud snoring. 34 A smartwatch alert can flag it, but in validation testing the alerts missed about a third of moderate to severe cases, so no alert is not an all-clear. 35 Snoring, gasping, waking unrefreshed, or heavy daytime sleepiness deserves a test, and a home sleep test is a guideline-accepted way to diagnose many cases. 36

For men: the testosterone night shift

We hear this from men on testosterone therapy all the time: the days got better, and the nights did not. Sleep and testosterone are tied together more tightly than most men realize.

Testosterone is built in your sleep. In one small study of ten young men, a week of five-hour nights lowered daytime testosterone by 10% to 15%. For scale, the authors note that normal aging lowers testosterone by about 1% to 2% a year. 37 Missing a full night clearly lowers testosterone. A few short nights have given mixed results across studies. 38

Apnea and low testosterone are tangled together, mostly through weight. Apnea is linked to lower testosterone, most clearly when it is severe. 39 40 Treating the breathing with CPAP does not reliably raise testosterone. In men with obesity, losing weight does, in proportion to the weight lost. 41 42

This matters before and during testosterone therapy. Starting testosterone can temporarily worsen breathing during sleep in men with severe apnea. 43 The Endocrine Society recommends against starting testosterone therapy with untreated severe apnea, 44 and testosterone labels warn about apnea in men with risk factors. 45 That is why we look at your breathing before and during testosterone therapy.

Then there is the nightly report card. Fewer morning erections is one of the sexual symptoms most closely tied to low testosterone in middle-aged and older men. 46 Apnea is linked to erectile problems too, and treating it modestly improved erectile function scores in pooled studies. 47 48 If your mornings have changed, that is worth bringing up.

For women: the cycle, the transition, and beyond

Short sleep hits women’s metabolism, too. In one trial of 38 women, six weeks of about an hour and 20 minutes less sleep a night raised insulin resistance, changes in body fat did not explain it, and the effect was stronger after menopause. 49

Sleep shifts across the menstrual cycle. Some women sleep worse just before and during their period, and short sleep is linked to irregular cycles. 50 Progesterone has a calming effect, partly through breakdown products such as allopregnanolone that act on the brain’s main calming receptors. 51

Perimenopause is its own chapter. Sleep problems become more common, and night sweats measurably wake women up. 52 53 I wrote about the bigger picture in my first article.

Apnea is easy to miss in women. Compared with men, women with apnea more often report insomnia and fatigue, and it is more often missed. The risk rises after menopause. 34 54 Women with PCOS have much higher rates of sleep apnea, and the international PCOS guideline says to ask about symptoms and test when they fit. 55 56

Holistic Hacks & Functional Facts

Get light early, and keep evenings dim. In a small study, a week of camping by natural light moved people’s body clocks about two hours earlier, and in another, a weekend got about two thirds of the way there. 57 58 More bright light in the morning is linked to falling asleep faster and sleeping better. 59 Expert consensus is simple: bright days, dim light for a few hours before bed, and a dark bedroom. 60

Wake at the same time every day. Neal Rouzier, MD, teaches this one: the same wake time every morning, and no sleeping in to make up for a bad night. 61 The regularity research above points the same way.

Time the coffee and the nightcap. A noon caffeine cutoff works for many people. 30 A nightcap costs overnight recovery even when it helps you drift off. 29

Keep the room cool, and try a warm shower. A warm bath or shower one to two hours before bed helps people fall asleep faster by helping the body shed heat. 62

Block noise instead of adding it. A small 2026 lab study found pink noise cut dream sleep, and earplugs worked better against outside noise. 63

The supplements and trends, rated honestly.

What	The claim	What the evidence shows
Magnesium	The missing sleep mineral	Small, early evidence. Some people notice a difference. 64 65 Sprays and flakes lack absorption evidence. 66
Glycine	Deeper sleep	Three small trials. The big stacks online go far past anything tested. 67 68
Melatonin	A knockout pill	More a timing signal than a sedative, and it works better taken earlier. Labels are often inaccurate. 69 70
Ashwagandha	Lower cortisol, better sleep	A modest sleep benefit in small trials, and rare but serious liver injury has been reported. 71 72
Tart cherry	Natural melatonin	Small studies with mixed results. 73
Mouth tape	Better sleep and recovery	The evidence is early, from a few small studies. I am a fan for some healthy people who breathe easily through the nose, when it is appropriate. It is risky with undiagnosed apnea or a blocked nose, so if you are not sure you are a candidate, we should talk first. 74 75
Sleep trackers	Know your sleep stages	Good at spotting sleep, weaker at catching time awake and at stages, and chasing a score can make sleep worse. 76 77
Blue-light glasses	Protect melatonin	Very low certainty. Dimming the room is better supported. 78

Where medicine fits. Hormone therapy can help some women sleep, especially when night sweats are what wakes them. It is one tool, and its benefits and risks are individual. 79 At Rez, testosterone therapy comes with a breathing check. And for adults with obesity and moderate to severe apnea, tirzepatide became the first medicine approved for apnea in December 2024, for use alongside diet and activity. In two trials it cut apnea events by about 20 to 24 an hour more than placebo at one year. 80 81 The benefit followed weight loss and took about 20 weeks to separate from placebo, and sleep specialists treat it as an add-on to CPAP, not a replacement. 82 83 A pill for people who cannot use CPAP is in late-stage trials and is not approved yet. 84

Bring your nights to the conversation

A week or two of simple notes, sometimes called a sleep diary, makes any conversation with a clinician more useful:

Wake times, and whether they land at the same hour most nights.
What seems to cause the waking: heat, a racing mind, the bathroom, or nothing obvious.
Snoring or gasping that someone else has noticed, or sleep that never feels restful.
Evenings, including light, caffeine, alcohol, and late meals.
Changes you have noticed: energy, mood, drive, morning erections, or your cycle.
What you have already tried, including supplements, sleep medicines, and trackers.

Sleep is not a reward for finishing everything else. It is where the work gets done.

Every hack and fact above is free, and I hope you try them. Morning light, a steady wake time, a cooler room, and an honest look at the nightcap can change a lot on their own. But a list cannot read your labs, check your breathing, or notice that your testosterone, your cycle, your thyroid, or your stress hormones have shifted. It cannot build a plan around your history, and it cannot adjust that plan as your body responds. That is where my expertise comes in. I ask every client about sleep. We investigate the whole picture, your nights included, then build a plan that fits you and monitor it closely. Sometimes that means hormone therapy, testosterone therapy with a breathing check, or help with weight. Sometimes it is something simpler than you expected. Either way, you do not have to figure it out alone.

Feel like yourself again. That is the goal, and it starts at night.

Book your comprehensive consultation, or explore care for men and women at Rez.

About Kellie

Kellie Marsoobian, FNP-C, is the founder and lead provider of Rez. She is Advanced BHRT certified through WorldLink Medical, having completed the Advanced Bioidentical Hormone Replacement Therapy course series taught by Neal Rouzier, MD.

This article is general education, not personal medical advice. A qualified clinician can help assess individual symptoms and discuss suitable care.

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