An excellent article. It may be worth adding one more fact: in the USA endocrinologists incorrectly assume a Gaussian distribution of values for all hormones across the population; this frequently leads to incorrect diagnosis in many cases because the assumption is that if you’re within a standard deviation of the mean then you’re fine.
A friend of mine was a long-time NFL linebacker. His normal testosterone level was at the far end of the bell-curve, so when his levels dropped to within a standard deviation of the assumed Gaussian mean, he felt awful: low energy, irritable, depressed, etc. Fortunately he consulted with a European endocrinologist who paid attention to his symptoms rather than to the blood panel results, and a testosterone patch restored his energy, mood, and sleep pattern within days. So while getting a blood panel is important, it’s not the most important diagnostic tool and people should be aware that in the USA this fact is not widely known.