Veedma Health Blog

Low testosterone affects sex, energy, body composition, mood, thinking, and sleep; spotting the full pattern gets you to the right tests sooner.

The relationship

Testosterone is a whole-body signal. It acts on brain, muscle, fat, blood, bone, and the vascular system. When levels fall, men can notice sexual and nonsexual changes that travel together as a pattern of hypogonadism — a state of low testosterone with symptoms that improve when levels are restored [1,2].

Large population data defined late-onset hypogonadism by three sexual symptoms that matter most clinically: libido loss (lower sexual desire), fewer morning erections (spontaneous erections on waking), and erectile changes (difficulty achieving or maintaining erections) in men with low measured testosterone [3].

Randomized trials show that treatment can improve sexual function and correct anemia (low red blood cell count) in many men, while effects on walking speed and vitality are modest and variable [4,5,10].

How it works

From brain signal to blood flow

Testosterone supports erection biology by maintaining nitric oxide signaling that relaxes penile blood vessels and by sustaining healthy erectile tissue. Much of the mechanistic evidence comes from animal and tissue studies, which show androgen effects on nitric oxide synthase and cavernous tissue; human evidence links very low levels with worse erectile performance [2,17].

Bioavailable hormone and SHBG

Sex hormone binding globulin is a carrier protein that binds testosterone. Higher SHBG leaves less free hormone available to tissues. Lower SHBG is common with obesity and insulin resistance; both lower total and free testosterone and raise the odds of metabolic syndrome [8,9].

Daily rhythm and morning testing

Testosterone follows a morning-peaking circadian rhythm — a daily biological cycle. Morning measurements are higher and more stable, which is why guidelines advise morning testing and repeating the test on a separate day [7,1].

Mood, motivation, and cognition

Trials and meta-analyses show mixed results. Some analyses report reduced depressive symptoms with treatment, while the Testosterone Trials found no improvement in objective cognitive testing in men with age-related memory impairment [18,15].

Clinical thresholds that guide action

Meta-analyses suggest symptomatic men with total testosterone below 350 ng/dL (about 12 nmol/L) are most likely to benefit from therapy. If total testosterone is borderline, add free testosterone; values below 100 pg/mL (about 10 ng/dL) support hypogonadism. In practice, use 350 ng/dL for total or 100 pg/mL for free as decision thresholds when symptoms persist [16,1].

Conditions linked to it

• Obesity and insulin resistance: Lower total and free testosterone track with higher waist size and metabolic syndrome; SHBG often falls as weight rises [8,9].
• Anemia: Low testosterone raises anemia risk. Treatment corrected anemia in many older men in randomized trials [5,6].
• Obstructive sleep apnea: Severe apnea associates with lower testosterone; CPAP does not reliably raise testosterone. Treatment decisions should weigh apnea severity and symptoms [13,14].
• Bone health: Treatment increased spine volumetric bone density and estimated strength over 12 months in the Testosterone Trials, though fracture reduction is unproven [19,4].

Limitations: Sleep apnea evidence shows association and small trials with mixed treatment effects; cognition findings are inconsistent across studies [13,14,15].

Symptoms and signals

These are common low testosterone symptoms described in guidelines and large trials [1,3]:

• Libido loss: Less interest in sex.
• Erectile changes: Softer or less reliable erections.
• Fewer morning erections: Noticeably fewer on waking.
• Orgasm difficulty: Harder to reach climax.
• Fatigue in men: Lower daytime energy and stamina.
• Slower workouts: Less strength gain and slower recovery.
• Weight gain in men: More abdominal fat despite similar diet.
• Low mood: More irritability or a flat, down mood.
• Brain fog: Trouble with focus or word finding.
• Poor sleep: Fragmented sleep or nonrestorative sleep that links to sleep and hormones.

What to do about it

1. Test correctly. Get two morning total testosterone tests on different days. If total is borderline, add free testosterone and measure SHBG. Review medicines, alcohol, and sleep. Screen for obesity and apnea when suggested by symptoms [1,7,13].
2. Match treatment to the pattern. If symptoms persist and levels meet thresholds, discuss lifestyle steps, apnea treatment if present, and testosterone therapy options. Trials show sexual function and anemia often improve, while gains in walking ability and cognition are limited or mixed [4,5,10,15].
3. Monitor. Recheck symptoms and labs after dose titration. Track hematocrit, lipids, and PSA as recommended. Adjust dose to physiologic range and address side effects early [1,2].

Myth vs Fact

• Myth: If erections still happen, testosterone is fine. Fact: Men with low testosterone can still have intermittent erections. Fewer morning erections are a stronger sex-specific clue in this context [3].
• Myth: Only libido matters. Fact: Clusters that include energy, body composition, mood, and sleep are common and clinically relevant [1,2].
• Myth: CPAP raises testosterone by itself. Fact: Reviews do not show a reliable rise after CPAP alone; treat apnea for health, but test hormones separately [9].
• Myth: Testosterone therapy fixes memory. Fact: Cognitive outcomes in large trials were neutral despite symptom gains in other areas [15].
• Myth: One lab is enough. Fact: Morning testing on two different days reduces false lows and guides better decisions [7,1].

Bottom line

Low testosterone is more than libido. A recognizable pattern of sexual, energy, mood, body, and sleep changes points to the right testing and a plan that blends lifestyle, sleep care, and targeted therapy when thresholds and symptoms align [1,16].