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Powerful And Dangerous

Like many cancer drugs, Opdivo is very powerful and potentially dangerous. It changes your immune system forever. In addition to killing cancer cells, Opdivo can attack any organ in your body during treatment, or even after it’s discontinued. One of the more well-known and common side effects of Opdivo is that it can kill your thyroid gland.

The main job of the thyroid gland is to make the hormone thyroxine, also known as T4 because it has four iodine molecules. The thyroid also makes the hormone triiodothyronine, known as T3 because it has three iodine molecules, but in smaller amounts, explains Cathy Doria-Medina, MD, an endocrinologist with HealthCare Partners Medical Group in Torrance, California. “The thyroid gland makes mostly T4, [and] the T4 has to be converted to T3, because T3 is the part of thyroxine that actually does the work,” she says.

The pituitary gland at the base of the brain controls hormone production in your body. It makes Thyroid-Stimulating Hormone (TSH), which tells the thyroid gland how much T4 and T3 to produce. The TSH level in your blood reveals how much T4 your pituitary gland is asking your thyroid gland to make. A normal range for TSH in most laboratories is 0.4 milliunits per liter (mU/L) to 4.0 mU/L. If your TSH levels are abnormally high, it could mean you have an underactive thyroid, or hypothyroidism. – everydayhealth.com

With that 1D, sequential, textual intro to the pituitary/thyroid/TSH/T3/T4 feedback control system in our bodies, here’s a simple, 2D visual representation:

Ever since William L. Livingston introduced me to the brilliant, but underappreciated, work of William Powers I have a tendency to think of the human body as a wondrous, hierarchical, interconnected, aggregation of thousands of little negative feedback control systems. Ah, but once again I digress. Time to kick out of enginerd mode and back into C-patient mode.

The graph below shows how my TSH level has varied over the past few months. Starting in May, my TSH level zoomed off the chart. The symptoms I started feeling were increased fatigue and increased sensitivity to cold.

Levothyroxine is a synthetic substitute for the T4/T3 hormones produced by the thyroid. Sometime in June, I started taking 25 mcg/day of Levothyroxine.  Since my TSH level is still way above the maximum “normal” level, my dosage has been bumped up to 75 mcg/day.

Part of the “fun” of having cancer is learning all about how different subsystems in the body work. Every time a new complication pops up, I research the subject in order to understand better what to expect and how to resolve the issue or ameliorate the symptoms.

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