Partial disassembly of cellular backbones give sperm a characteristic shape that is apparent in a conventional sperm analysis, at least in cases where sperm production continues at a reduced level. Blood cadmium levels can be measured by a clinical chemistry laboratory. Varicose veins in the testes are routinely identified by palpation or ultrasonography. The cadmium-sensitive types of sperm calcium ion channels can be distinguished by molecular testing. Other factors are likely to be involved in cadmium's reproductive effects.
Calcium acts as a secondary messenger in cells.
That is, it carries instructions from cellular surfaces to proteins deep within, starting, stopping or modulating cellular events like mRNA transcription. Genetic variations in these other proteins could conceivably make them more or less sensitive to changes in the signaling that cadmium can disrupt. Lead seems to affect a different pathway in sperm function. Progesterone, a molecule present in relatively high concentration in the mass of cells that accompany a fertile egg down a woman's Fallopian tubes, seems to act upon sperm through a protein on the sperm head that binds progesterone. The act of binding progesterone seems to prime sperm, so that they can react properly when they touch the egg.