Seasonal affective disorder hormones: How to tell SAD from low testosterone in men

SAD usually follows a repeatable fall-to-winter pattern and improves in spring, while low testosterone is more likely when symptoms are persistent, come with libido or erection changes, and are confirmed on repeat morning blood tests. If your symptoms do not cleanly follow the calendar, or they come with sexual or sleep changes, it is time to look at seasonal affective disorder hormones together and not as separate problems.

Key takeaways

• If symptoms persist past spring, or begin in your 30s to 50s, consider a hormone and thyroid workup in addition to screening for seasonal affective disorder.
• Two meta-analyses of placebo-controlled trials found that testosterone treatment reduced depressive symptoms.^{[1] [2]} The earlier one found a significant response in the subgroup with hypogonadism.^[1]
• When repeat morning tests confirm low testosterone with low or normal LH, the pattern points to secondary or functional hypogonadism. Testosterone therapy suppresses sperm production, so for men who want to preserve fertility, treatments that raise the body’s own testosterone are an option. Enclomiphene is one of them.
• A practical first step is a 14 day log of sleep timing, morning energy, libido, and mood. Pair it with repeat morning labs drawn between 07:00 and 11:00 that include total testosterone, free testosterone, LH, and FSH. Add TSH when thyroid disease is possible, and other tests such as estradiol, CBC, CMP, prolactin, or PSA for men 40 and older as indicated.
• Bright light therapy reduced symptoms of seasonal affective disorder in a meta-analysis of randomized trials.^[3] A poor response is a reason to look more broadly at sleep, thyroid function, and testosterone.

Why winter mood and male hormones get confused

Seasonal affective disorder, also called SAD, is a pattern of depression that recurs in winter and remits the following spring or summer.^[4] Male hormone problems can produce a similar symptom cluster, including fatigue, irritability, low motivation, heavier sleep, and social withdrawal. For that reason, winter low mood in a man calls for a broader clinical differential diagnosis rather than an assumption that the season is to blame.

According to a 2003 review in Chronobiology International, SAD affects an estimated 1 to 3% of adults in temperate climates, and the mechanisms behind it are still incompletely understood.^[4] Testosterone and cortisol follow daily rhythms of their own. Both are normally highest in the morning, and both are sensitive to sleep, which winter often shifts later and lengthens.

Studies of seasonal variation in men’s testosterone have produced mixed results, so a winter dip is not a reliable explanation for a low reading. Winter does not cause hypogonadism, which is clinically low testosterone with symptoms. At most, seasonal changes in sleep, light, and activity may make a borderline level more noticeable.

How seasonal affective disorder hormones interact

Light, circadian rhythm, and melatonin

Circadian rhythm is the internal 24 hour clock that times sleep, wake, body temperature, and hormone release. The main signal that sets this clock is light reaching the retina, the light sensing tissue at the back of the eye, and winter days provide less of it. One explanation for SAD, the phase-delay hypothesis, holds that patients’ circadian rhythms run late relative to their sleep and wake cycle. The hypothesis predicts that symptoms improve when those rhythms are shifted earlier, and there is some experimental support for this.^[4]

Melatonin is a hormone released in darkness that signals “biological night.” It is one proposed link between short days and the longer sleep and low daytime energy seen in SAD, although its exact role is not settled. Sleep also matters for testosterone. In a small 2011 study in JAMA, ten young healthy men had their sleep restricted to five hours a night for one week.^[5] Their daytime testosterone levels were 10 to 15% lower than after normal sleep.^[5]

Serotonin and dopamine are mood chemistry that hormones can influence

Serotonin is a neurotransmitter that supports mood stability. Dopamine is a neurotransmitter tied to motivation and reward. A variety of research approaches have demonstrated dysfunction in the serotonin system in SAD. Along with low mood, the condition typically brings increased appetite and longer sleep in winter.^[4]

Low testosterone can also present with low mood. A 2009 meta-analysis in the Journal of Psychiatric Practice pooled seven double-blind, placebo-controlled trials (364 patients) in people diagnosed with a depressive disorder.^[1] Testosterone improved Hamilton depression scores compared with placebo, with significant effects in the subgroups with hypogonadism and with HIV/AIDS.^[1] A 2019 meta-analysis in JAMA Psychiatry of 27 randomized trials including 1,890 men found a small but significant reduction in depressive symptoms (Hedges g 0.21).^[2] Its authors called for more trials that use depression as the primary end point.^[2] Testosterone is therefore not a general antidepressant, but when low testosterone is part of a man’s winter depression, correcting it may help.

Testosterone and cortisol follow daily rhythms

Cortisol is the main stress hormone. It helps regulate alertness, blood sugar, and stress tolerance, and it normally peaks shortly after waking. Later and longer winter sleep, and circadian misalignment in general, can change the timing of that rise. Testosterone is also highest in the morning, which is why the time of a blood draw matters.

The 2018 American Urological Association guideline recommends diagnosing testosterone deficiency only when symptoms are present and two early morning total testosterone measurements taken on separate occasions are low.^[6] It treats a total testosterone below 300 ng/dL as a reasonable cut-off and advises measuring LH in men with low testosterone.^[6] Cut-offs differ between guidelines and clinics, so the symptom history and repeat morning labs matter as much as any single number.

Thyroid hormones set the pace for energy and mood

Thyroid hormones help regulate metabolism, temperature, and brain function. The classic symptoms of hypothyroidism, or low thyroid function, are fatigue, lethargy, weight gain, and cold intolerance.^[7] People with thyroid disorders are also more prone to depressive symptoms.^[8] Because these symptoms overlap with winter depression, hypothyroidism that worsens during a sluggish winter can be mistaken for SAD.

According to a 2012 review in the Journal of Thyroid Research, the relationship runs both ways.^[8] Thyroid disorders raise the likelihood of depressive symptoms, and depression can come with subtle thyroid abnormalities. Thyroid hormone also appears to speed and enhance the response to antidepressants.^[8] A 2024 seminar in The Lancet notes that hypothyroid symptoms are non-specific, so the diagnosis is made on blood tests.^[7] Levothyroxine improves symptoms in most patients, although about 10% have persistent symptoms despite normal thyroid tests.^[7]

Conditions that can look like SAD in men

Clinicians usually start by confirming the pattern: depressive episodes that begin in fall or winter and remit in spring or summer.^[4] Standard diagnostic criteria also require that this pattern has held for at least two consecutive years and is not better explained by another condition. Clinicians also take a full mood history, including screening for bipolar disorder. They review medications and alcohol use and assess sleep timing and sleep quality.

Testing helps separate look alikes when the story is not clearly seasonal, or when sexual symptoms, major sleep disruption, or unexplained weight or temperature changes are present. Common next steps include repeat morning testing from 07:00 to 11:00 with total testosterone, free testosterone, LH, and FSH. TSH with free T4 is added when thyroid disease is suspected, along with a targeted sleep evaluation, including home sleep apnea testing or polysomnography when indicated. Several findings point away from SAD as the primary driver: consistently low morning testosterone on repeat testing, elevated TSH with low free T4, or marked obstructive sleep apnea.

• Seasonal affective disorder: Recurrent winter depression that remits in spring or summer, often with increased appetite and longer sleep.^[4]
• Male hypogonadism: Clinically low testosterone with symptoms such as depressed mood, irritability, low motivation, and low libido. In meta-analyses of placebo-controlled trials, testosterone treatment reduced depressive symptoms.^{[1] [2]} The 2009 analysis found a significant effect in its hypogonadal subgroup.^[1]
• Thyroid dysfunction: Hypothyroidism causes fatigue, and levothyroxine improves symptoms in most patients.^[7] Thyroid disorders are also associated with depressive symptoms.^[8]
• Chronic stress with altered cortisol dynamics: Sleep related changes in cortisol rhythm can affect energy, mood stability, and stress tolerance.
• Sleep and circadian disorders: Delayed sleep timing, insomnia, obstructive sleep apnea, and irregular schedules can worsen winter mood and reduce daytime energy and motivation.

Seasonal shifts in hormone levels, where they occur, are patterns seen at the group level. They do not prove that hormones cause depression in an individual. Symptom correlation and diagnostic testing are still needed to decide what is clinically meaningful for you.

Symptoms and signals to watch for

SAD and hormone driven mood changes overlap, so the goal is not self diagnosis but noticing clues that point beyond the season.

Focus on differentiators. SAD tends to be strongly seasonal, with late fall onset and spring relief, and often comes with hypersomnia and low daytime energy. Low testosterone is more suspicious when symptoms persist outside winter and are paired with reduced libido, fewer morning erections, or new erectile changes. Insomnia or early morning awakening can occur in many depressive states, but if you are not improving by spring, a purely seasonal pattern is less likely. Seek urgent evaluation if you have suicidal thoughts, feel unsafe, or your symptoms cause severe functional impairment, for example missing work, stopping eating, or being unable to care for yourself.

• Calendar pattern: SAD recurs in winter and improves in spring or summer.^[4]
• Symptoms that do not fully lift in spring: This is a common red flag for non-seasonal drivers such as low testosterone or thyroid dysfunction.
• Low libido or sexual functioning changes: Reduced desire, fewer morning erections, or a new drop in sexual performance alongside low mood can point toward testosterone involvement.
• Heavier sleep but worse energy: Longer sleep is typical of SAD,^[4] but fatigue and lethargy are also classic symptoms of hypothyroidism.^[7]
• Increased irritability and lower stress tolerance: This can be a depression symptom, a sign of disrupted sleep and cortisol rhythm, or part of androgen deficiency in men.
• Age and timing: If symptoms begin in your 30s, 40s, or 50s, do not assume it is “just winter.” In a long-term study of healthy men, total testosterone and the free testosterone index declined gradually with age.^[9] Hypothyroidism is also a common condition, and its symptoms overlap with low mood and fatigue.^[7]
• Little response to light therapy or vitamin D: If you try standard seasonal strategies and feel no meaningful change, the case for a hormone and sleep evaluation is stronger.

What to do about it

You do not need to choose between “it is SAD” and “it is hormones.” A practical approach in men is to evaluate both in parallel, then treat the dominant driver.

1. Step 1: Confirm the pattern and get the right labs Start with a 14 day log of sleep and wake times, morning energy, mood, cravings, training performance, and libido. Then schedule repeat morning blood work collected from 07:00 to 11:00. Every time testosterone is being evaluated, include total testosterone, free testosterone, LH, and FSH. Free testosterone can be measured by equilibrium dialysis or calculated from total testosterone, SHBG, and albumin. Depending on age and context, add estradiol, CBC, CMP, PSA if you are 40 or older, and prolactin when indicated. Hypothyroid symptoms are non-specific, so thyroid status is judged on blood tests: TSH, with free T4 when thyroid disease is suspected.^[7]
2. Step 2: Match treatment to the diagnosis, not the season According to a 2005 meta-analysis of randomized trials in the American Journal of Psychiatry, bright light treatment reduced depression severity in seasonal affective disorder (eight studies, effect size 0.84).^[3] Dawn simulation also reduced it (five studies, effect size 0.73), and both effects were comparable to those in most antidepressant drug trials.^[3] In classical light therapy, the person sits in front of a light box delivering 2,000 to 10,000 lux for 30 to 120 minutes a day during winter.^[4] If repeat labs point to testosterone deficiency, treatment depends on the type. In secondary or functional hypogonadism, LH is low or normal and the testes are intact. Options that raise the body’s own testosterone, such as enclomiphene, can therefore keep sperm production going. Testosterone therapy, such as testosterone cypionate injections, is a standard treatment for primary hypogonadism, where the testes themselves are failing. It suppresses sperm production, so the AUA guideline advises against it for men who are trying to conceive.^[6] If thyroid tests confirm hypothyroidism, levothyroxine restores thyroid function and improves symptoms in most patients.^[7]
3. Step 3: Monitor and adjust Use bright light therapy for confirmed SAD, and add psychotherapy or antidepressants when the depressive syndrome requires them. If testosterone therapy is started, the AUA guideline recommends checking hematocrit before treatment and periodically during it.^[6] Hormones change with sleep, weight, stress, and season. Plan repeat labs and a symptom review, then adjust treatment based on objective results and how you actually feel.

Veedma offers testing that includes total and free testosterone measured by LC-MS/MS together with LH and FSH, or a review of labs you already have, with results interpreted by licensed providers across the U.S. When appropriate, treatment is enclomiphene or a tablet combining enclomiphene and tadalafil. Enclomiphene is not an FDA-approved drug; it is prescribed after a provider confirms the diagnosis and is compounded by a licensed U.S. pharmacy.

Myth vs fact

Myth: If I feel depressed in winter, it is definitely seasonal affective disorder.

Fact: SAD is defined by a recurring winter pattern with remission in spring or summer.^[4] Other conditions can produce similar symptoms. Thyroid disorders make depressive symptoms more likely,^[8] and in placebo-controlled trials, testosterone treatment reduced depressive symptoms in depressed men with hypogonadism.^[1]

Myth: Light therapy not working means I am just ‘treatment resistant.’

Fact: Bright light is effective for SAD in randomized trials.^[3] A poor response is a reason to recheck the diagnosis, including sleep, thyroid function, and testosterone, before calling it treatment resistance.

Myth: Testosterone therapy is an antidepressant.

Fact: Testosterone is not a general antidepressant. Meta-analyses found a modest reduction in depressive symptoms with testosterone treatment,^{[1] [2]} and the 2009 analysis found a significant effect in the subgroup with hypogonadism.^[1]

Myth: If my testosterone is ‘normal’, hormones cannot be involved.

Fact: Symptoms, free testosterone, sleep, and thyroid status all matter. A normal total testosterone can coexist with low free testosterone when SHBG is high, and thyroid disease can cause similar symptoms on its own.

Myth: All testosterone treatment shuts down fertility.

Fact: Exogenous testosterone suppresses sperm production, and the AUA guideline advises against it for men who are trying to conceive.^[6] Secondary or functional hypogonadism can instead be treated by raising the body’s own LH and FSH, which is designed to keep sperm production going. Enclomiphene works this way.

Bottom line

In men, winter depression is not always seasonal affective disorder. SAD is suggested by repeatable fall or winter onset, spring remission, and improvement with bright light therapy. Hypogonadism is suggested by symptoms that last year round or persist into spring, together with libido or erection changes. It is confirmed only with repeat morning testing between 07:00 and 11:00 that includes total testosterone, free testosterone, LH, and FSH. See a clinician if your pattern is unclear, symptoms are severe, or you notice sexual or major sleep changes. The plan may include light therapy for confirmed SAD, sleep treatment, psychotherapy, and hormone or thyroid management.

References

1. Zarrouf FA, Artz S, Griffith J, et al. Testosterone and depression: systematic review and meta-analysis. J Psychiatr Pract. 2009;15:289-305. PMID: 19625884
2. Walther A, Breidenstein J, Miller R. Association of Testosterone Treatment With Alleviation of Depressive Symptoms in Men: A Systematic Review and Meta-analysis. JAMA Psychiatry. 2019;76:31-40. PMID: 30427999
3. Golden RN, Gaynes BN, Ekstrom RD, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry. 2005;162:656-62. PMID: 15800134
4. Magnusson A, Boivin D. Seasonal affective disorder: an overview. Chronobiol Int. 2003;20:189-207. PMID: 12723880
5. Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305:2173-4. PMID: 21632481
6. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018;200:423-432. PMID: 29601923
7. Taylor PN, Medici MM, Hubalewska-Dydejczyk A, et al. Hypothyroidism. Lancet. 2024;404:1347-1364. PMID: 39368843
8. Hage MP, Azar ST. The Link between Thyroid Function and Depression. J Thyroid Res. 2012;2012:590648. PMID: 22220285
9. Harman SM, Metter EJ, Tobin JD, et al. Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging. J Clin Endocrinol Metab. 2001;86:724-31. PMID: 11158037