If you're feeling more tired than usual, struggling with mental clarity, weight gain, or a drop in libido, testosterone could be part of the picture, but the cause of low testosterone isn’t always obvious.
There is quite a bit of coverage focused on the Top 5 Causes of Testosterone Decline:
- Chronic stress and elevated cortisol
- Poor sleep quality and disrupted testosterone rhythms
- Visceral fat and insulin resistance
- Exposure to environmental toxins
- Nutrient deficiencies in key cofactors like zinc, magnesium, and vitamin D
These factors account for the majority of testosterone decline I see clinically. However, some cases don’t fully resolve even after addressing those core issues, suggesting deeper, often overlooked causes.
Below are four lesser-known but clinically important contributors to testosterone dysfunction, along with the physiological science behind each.
1. Subclinical Hypothyroidism or Low Free T3
Thyroid hormones, especially triiodothyronine (T3), play a direct role in regulating enzymes responsible for converting cholesterol into testosterone. Even in men with normal TSH, low or borderline free T3 levels can impair this conversion process and suppress testosterone output.
Low thyroid function may also lead to:
- Reduced sex hormone-binding globulin (SHBG), impacting free testosterone
- Diminished luteinizing hormone (LH) output
- Shared symptoms with low testosterone (e.g. fatigue, mood decline, reduced libido)
Research from Krassas et al. (2008) demonstrated that men with even mild thyroid dysfunction had lower testosterone and poorer sexual function compared to euthyroid controls.
2. Elevated Prolactin (Hyperprolactinemia)
Prolactin, typically associated with lactation, plays a suppressive role in male hormone signalling. Elevated prolactin inhibits the hypothalamic release of gonadotropin-releasing hormone (GnRH), which reduces both LH and FSH, ultimately lowering testosterone production in the testes.
Common causes of elevated prolactin include:
- Stress (physical or emotional)
- Pituitary microadenomas
- Certain medications (especially SSRIs, antipsychotics, and opiates)
- Elevated estrogen levels
Because prolactin is not often included in standard hormone panels, this issue is frequently missed in men with unexplained low testosterone and low or normal LH/FSH.
3. Liver Dysfunction and Estrogen Overload
The liver is central to hormonal regulation. It metabolizes estrogen, produces SHBG, and governs cholesterol availability, the foundational precursor for all steroid hormones, including testosterone.
If liver detoxification pathways are impaired due to:
- Non-alcoholic fatty liver disease (NAFLD)
- Alcohol consumption
- Poor bile flow
- Toxin accumulation
Then testosterone production can falter. At the same time, estrogen may build up, leading to a condition often called “estrogen dominance,” which suppresses the hypothalamic-pituitary-gonadal (HPG) axis through negative feedback.
Men with impaired liver function often show:
- Elevated estrogen metabolites
- Lower SHBG and total testosterone
- Decreased clearance of inflammatory markers that also suppresses Leydig cell function
4. Undiagnosed Sleep Apnea
Testosterone production is highest during deep sleep, specifically in slow-wave and REM stages. Obstructive sleep apnea (OSA) disrupts both the architecture of sleep and oxygen delivery to the testes during these critical stages.
Sleep apnea also increases nocturnal cortisol, reduces melatonin signalling, and activates the sympathetic nervous system, all of which can suppress testosterone.
Clinical research has shown that:
- Men with untreated moderate to severe OSA often have morning testosterone levels 20–30% lower than controls
- Testosterone production improves significantly after consistent use of CPAP (continuous positive airway pressure) therapy
Despite this, sleep apnea remains underdiagnosed in men presenting with fatigue, weight gain, and hormonal complaints.
Are you concerned that you may have undiagnosed sleep apnea? NutriChem offers at-home sleep apnea tests. Contact our clinic for more information and to pick up a test.
Advanced Lab Testing at NutriChem
When men present with symptoms of low testosterone but normal basic labs, I expand our diagnostic testing to investigate these under-recognized contributors. Depending on the case, we may assess:
- Free T3, reverse T3, and thyroid antibodies
- Serum prolactin and pituitary hormones
- Comprehensive liver function markers and estrogen metabolites
- Sleep apnea via an at-home test.
This deeper investigation often reveals the missing piece of the hormonal puzzle, one that allows us to move from short-term management to true restoration of health.
Recap: Common vs. Lesser-Known Causes of Low Testosterone
Conclusion: Connecting the Dots in Men’s Hormone Health
Low testosterone is rarely due to just one cause. While stress, poor sleep, weight gain, and nutrient depletion are responsible for most cases, many men continue to experience symptoms even after these areas are addressed.
That’s where a functional and integrative approach becomes critical. Using detailed lab assessments, careful history, and systems-based physiology can uncover the deeper roots of hormonal dysfunction.
If you’re experiencing symptoms of low testosterone and haven’t found clear answers, I invite you to reach out. Your hormones are messengers. When they’re out of balance, they’re trying to tell you something important. Let’s listen and restore that balance naturally and scientifically
