Low testosterone

A factory with a broken order system

Imagine a testosterone factory (the testis) that makes the product only when it receives a phone order (LH signal from the pituitary). In primary hypogonadism, the factory's machinery is broken—the order arrives (LH is high) but the factory cannot produce, like a plant with busted assembly lines. In secondary hypogonadism, the phone system itself is dead—nobody is calling to place an order (LH is low), like a factory that sits idle because the sales office burned down. Either way, no product ships. The delivery trucks (bloodstream) are ready to haul testosterone everywhere (muscles, bones, brain), but without product, nothing gets delivered. The customer towns (muscles, bones, brain cells) start to decay because the building material never arrives. The key difference: in primary failure, you hear the phone ringing but nothing happens; in secondary failure, the phone never rings at all.