The reason why Barnes’ paper showing that desiccated thyroid lowering cholesterol levels and seeming to prevent cardiovascular disease isn’t cited is because he was basically making his patients hyperthyroid. Lower cholesterol levels occur in hyperthyroidism.
There is a doctor I know of in California who gives his patients supra-physiological levels of T3 hormone (cytomel) to increase their metabolism, to help them lose weight, and to lower their cholesterol levels. It basically suppresses the thyroid’s own production of hormone. In the short term, it works. It’s brilliant. But it’s crazy. We have no idea what the long-term consequences are. And since I’m pretty sure he’s not running a study on it, we won’t.
The TSH test is actually very accurate. Third generation TSH assays are able to detect 0.02 mIU/L or less.
The problem is the way TSH testing levels are used without regard for the actual thyroid hormone levels. The relationship between TSH, T4, and T3 is much more complicated than it seems.
A good explanation of the latest research into it is here: https://www.researchgate.net/publication/263321383. The title of the paper is “Homeostatic equilibria between free thyroid hormones and pituitary thyrotropin are modulated by various influences including age, body mass index and treatment.”