Fatigue, Low Libido, Brain Fog — Is It Low T or Something Else?

## The Symptom Overlap Problem\n\nThree of the most common low-T symptoms — fatigue, low libido, and brain fog — are also the hallmarks of hypothyroidism, major depressive disorder, and obstructive sleep apnea (OSA). Ruling these out before attributing symptoms to low T is essential.\n\n## Sleep Apnea\n\nOSA disrupts REM sleep and suppresses testosterone production. A man sleeping 7 hours but waking exhausted with morning headaches should evaluate for sleep apnea before pursuing TRT.\n\n**Checklist:** Do you snore? Wake gasping? Feel unrested after 8 hours?\n\n## Hypothyroidism\n\nLow thyroid hormone causes fatigue, weight gain, low libido, and brain fog — identical to low T. TSH, free T3, and free T4 testing rules this out.\n\n**Checklist:** Cold intolerance? Constipation? Dry skin? Family history of thyroid disease?\n\n## Depression\n\nMelancholic depression and low T are bidirectional — each can cause the other. The PHQ-9 is a validated 9-question screen.\n\n**Checklist:** Anhedonia (inability to feel pleasure)? Hopelessness? Suicidal ideation?\n\n## How to Approach Diagnosis\n\n1. **Start with a sleep study** if snoring or poor sleep quality is present\n2. **Add thyroid panel** (TSH, free T3, free T4, TPO antibodies)\n3. **Include testosterone panel** (total, free, SHBG, E2)\n4. **Consider depression screening** if mood symptoms predominate\n\nTreating the wrong cause is expensive and delays recovery. Getting all four evaluated simultaneously is the most efficient path.