The Steriodogenesis Pathway is a nice reference.
However, in real life, the primary question to ask is where are the hormones being produced and which of the products end up in the bloodstream.
For example, the brain produces a lot of pregnenolone and DHEA for its own use - more than any of the other neurotransmitters in the brain. But, these generally are kept in the brain rather than released as a signal to the rest of the body.
Almost all of the DHEA in the blood is from the adrenal glands. 5 % of
testosterone is produced by the adrenal glands. This
testosterone is then converted outside the adrenals to
DHT and Estradiol. DHEA can be later converted to testosterone then later
DHT or Estradiol.
The testes produce 95% of the testosterone measured in the blood. Testosterone is later converted to Estradiol or
DHT. Progesterone is the primary precursor to testosterone in the testes - not DHEA.
Thus for the most part, prior to supplementation, DHEA and Testosterone levels are going to be independent of each other. One is made by the adrenals, the other primarily by the testes.
Since each organ pumps out a different mixture of signals, the problem is not so much a blockage, but whether or not that particular organ is being signaled to make its products.
Rarely would a person be missing some enzyme to cause a blockage in production. Thus whether or not there is a blockage is not the correct answer.
Rather, it is a matter of whether or not that particular organ is capable of producing the range of products it is suppose to (e.g. primary hypogonadism) or whether or not it is receiving the appropriate and enough of the signal to product its products (e.g. secondary hypogonadism).
DHEA is a poor
test. It varies wildly from one moment to the next. DHEA-sulfate is a much more stable and useful
test.
High DHEA-s levels generally occur in response to stress. The younger the person, the higher DHEA can go since the layer making it is thicker in a young person compared to older person. If DHEA is high, then its most frequent metabolite can also be expected to be high. ACTH is produced in response to stress. This triggers output from the adrenal glands in a shotgun manner. Thus Cortisol, Progesterone, Pregnenolone, Testosterone, DHEA-s would be expected to increase in output from the adrenal gland in response to stress.