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Why Can’t My Doctor Find My Thyroid Problem?
Many patients experience fatigue, weight gain, cold intolerance, and brain fog despite being told their thyroid tests are “normal.” This article explains why thyroid disease is frequently missed, how temperature, genetics, inflammation, diet, and hormone conversion affect symptoms, and why a normal TSH does not rule out clinically meaningful hypothyroidism. Understanding thyroid function beyond basic labs often leads to answers patients have been seeking for years.

David Stephen Klein, MD FACA FACPM
3 days ago6 min read


Microplastics and Human Health: What Medicine Is Beginning to Understand.
Microplastics and nanoplastics have emerged as a previously unrecognized but increasingly relevant source of chronic environmental exposure. Once thought to be biologically inert, these particles—derived from degraded consumer plastics and industrial materials—are now routinely detected in human blood, stool, lung tissue, placenta, breast milk, and even atherosclerotic plaques. Their presence in these tissues challenges long-standing assumptions about plastic safety and raise

David S. Klein, MD FACA FACPM
4 days ago5 min read


Persistent Fatigue Is Not a Diagnosis
Persistent fatigue is not a diagnosis but a signal of underlying physiologic imbalance. Chronic low energy is often driven by overlooked metabolic dysfunction, hormone signaling abnormalities, sleep disruption, immune activation, or autonomic imbalance—frequently despite “normal” labs. A systematic, physician-led evaluation can uncover reversible causes and restore vitality rather than merely suppress symptoms.

David S. Klein, MD FACA FACPM
Jan 284 min read


Vitamin D is a Hormone
Vitamin D is commonly thought of as a simple nutrient, but medically it functions as a steroid hormone with effects far beyond bone health. Unlike true vitamins, vitamin D is synthesized in the skin, activated through the liver and kidneys, and acts on receptors throughout the body to regulate gene expression. This hormonal role explains its influence on immune function, muscle strength, cardiovascular health, and brain function. Because deficiency is widespread and supplemen

David S. Klein, MD FACA FACPM
Jan 244 min read


What is a Vitamin?
What is a vitamin? A physician explains vitamin definitions, deficiencies, supplementation, and why vitamin D is actually a hormone.

David S. Klein, MD FACA FACPM
Jan 134 min read


THC, REM Sleep, and the Quiet Disruption of Sleep Architecture
THC may shorten sleep onset, but research shows it suppresses REM sleep and disrupts normal sleep architecture. Over time, this can impair memory, mood, and restorative sleep—especially with nightly use. Understanding the difference between sedation and healthy sleep is critical.

David S. Klein, MD FACA FACPM
Jan 55 min read


THE HIDDEN CAUSES OF PERSISTENT FATIGUE: A PHYSICIAN’S GUIDE TO OVERLOOKED METABOLIC AND ENDOCRINE DISORDERS
Chronic fatigue often signals hidden metabolic or endocrine disorders. Learn the overlooked causes—from thyroid and iron issues to insulin resistance and mitochondria.

David S. Klein, MD FACA FACPM
Dec 24, 20254 min read


Testosterone Replacement Therapy: Why I Often Prefer the Transdermal Approach
Physician explains benefits of transdermal testosterone therapy, who qualifies, and why regular lab monitoring is essential for safe, effective treatment.

David S. Klein, MD FACA FACPM
Dec 9, 20259 min read


Peptide therapy: promise, pitfalls and what patients should know
Peptides are short amino-acid chains that act as highly specific signaling molecules and have become a major class of modern therapeutics. More than 80 peptide drugs are approved worldwide, including insulin, incretin analogues such as GLP-1 receptor agonists, vasopressin analogues and linaclotide. These agents provide effective, targeted therapy in endocrine, metabolic, gastrointestinal and oncologic indications, supported by robust randomized clinical trials and rigorous ma

David S. Klein, MD FACA FACPM
Dec 5, 20258 min read


Lactoferrin Containing Colostrum: Targeted Support for Sleep, Immunity, and Respiratory Health
Lactoferrin-rich colostrum occupies a unique niche at the intersection of mucosal immunity, systemic inflammatory control, and sleep regulation. By combining the broad matrix of colostrum with the targeted antiviral, antibacterial, and immunomodulatory activity of lactoferrin, these preparations can reduce the burden of upper respiratory infections, support resilient immune function, and modestly improve sleep quality in selected populations. As with any therapeutic nutrient,

David S. Klein, MD FACA FACPM
Dec 1, 20256 min read
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