The Most Prescribed Drug on the Planet

Levothyroxine (T4) aka Synthroid has been a mainstay in the pharmaceutical industry for decades due to the high prevalence of hypothyroidism and until this year (overthrown by Lipitor, a statin) was the most prescribed drug on the planet.

What is hypothyroidism? Why has Lipitor now taken the gold medal? And are the conditions of hypothyroidism and elevated cholesterol related?

Let’s have a look…

The thyroid gland is the top level, energy management system of the body. It interfaces with the mitochondria bidirectionally taking and giving cues from these energy producers to modulate production of thyroid hormone. Put simply, if mitochondrial production is low this signal tells the thyroid to produce less hormones and vice versa.

Many factors go into this signaling but the important takeaway is that the thyroid system and your mitochondria determine your metabolic rate and energy production.

One of the most common symptoms of hypothyroidism is feeling cold. This could be mild exhibited by cold fingertips and toe tips to a whole body chill while its 72 F.

One of the products of good mitochondrial function is heat so in the case of hypothyroidism, mitochondrial function has slowed down and in turn produces less heat. This problem is so ubiquitous that the average human body temperature in the USA has decreased 1.5 degrees Fahrenheit in the last 100 years!

If you went to go to your doc and told them about being cold, hair falling out, brittle nails, poor digestion, trouble sleeping, general fatigue, they’d order a thyroid TSH blood test. If its elevated, they’d prescribe you levothyroxine (T4) aka Synthroid. You’d diligently take your meds and go back to the doc. They’d order your TSH again and in a typical case, TSH would normalize however you’d likely feel they same or worse. Why?

There are actually 4 types of thyroid hormone but the most important to our discussion are T4 (storage form) and T3 (active form). The numbers indicate how many iodine atoms are attached to the thyroid hormone.

The production of active thyroid, T3, comes at the end of a cascade of signaling from the mitochondria to the hypothalamus, to the pituitary, to the liver. The liver is the primary location for converting the storage T4 form made in the thyroid gland into the active T3 form. If the liver is bogged down through detoxifying other things (which I’ll write about next week), it will inhibit the Deiodinase Type 1 enzyme (D1) that makes active T3. This causes the typical hypothyroid symptoms and slows down mitochondrial production.

Guess what else happens when your liver doesn’t convert T4 to T3? Cholesterol increases in the blood! This is well documented in the medical literature.

One of the primary roles of cholesterol is as a substrate for steroid (sex) hormones.

T3 has long been known to increase cell LDL receptors. These receptors are essentially docking stations for LDL-C (measured in your lipid panel). LDL-C carries cholesterol around your blood stream and then docks to the cell receptor to offload the cholesterol into the cell.

Once inside the cell, a protein called StAR shuttles cholesterol into the mitochondria of the ovaries, testes, adrenal and brain. This process produces crucial health and wellbeing hormones like pregenenolone, progesterone, testosterone, and DHEA.

The biochemical that determines the efficiency of the StAR protein is T3. So, if you don’t have enough T3 (and cholesterol), you will have lower sex hormones.

Typically, if your LDL-C is high your doc will prescribe a statin to lower it (enter Lipitor). It’s also common now to recommend statins prophylactically and without looking at blood lipids first.

But from what you just learned, LDL-C is most accurately viewed as a marker of conversion of cholesterol into the pro-longevity, pro-metabolic hormones.

Jonathan