Metabolite

Pregnenolone after CYP17A1 hydroxylates it. One step from DHEA.

Steroid intermediate measured clinically to screen for 21-hydroxylase deficiency.

A metabolite of DHT with no androgen receptor activity of its own. It acts on the GABA-A receptor instead, which is how an androgen ends up changing anxiety and sleep without touching the androgen receptor at all.

Where carbohydrate, fat and protein breakdown all converge before entering the Krebs cycle.

Spent ATP, waiting for a phosphate back.

Carries nitrogen from muscle to liver, where it is handed to alpha-ketoglutarate by ALT.

Krebs cycle intermediate and the nitrogen acceptor in every transamination.

Accumulates when energy is scarce. Rising AMP is what activates AMPK.

Sits one step below testosterone and one step below oestrone. Aromatase can take it either way.

Amino acid AST moves nitrogen onto. Also feeds the urea cycle.

The inactive partner of cortisol. HSD11B1 switches it on in tissue, HSD11B2 switches cortisol off.

Buffers ATP in muscle and brain by holding a spare phosphate group.

The unsulfated adrenal androgen. Circulates mostly as its sulfate, DHEA-S, which is what labs measure.

What is left after a second iodine comes off T3 or reverse T3. Largely a clearance product.

Neurotransmitter for motivation and movement, and the direct precursor of noradrenaline.

Adrenaline. The end of the catecholamine chain and the fastest arm of the stress response.

The weaker oestrogen, and the dominant one after menopause because adipose aromatase keeps making it.

The hub of amino-acid nitrogen handling and the main excitatory neurotransmitter.

The smallest amino acid, a third of collagen by residue count, and a substrate for glutathione.

The committed precursor in cholesterol synthesis. HMGCR reduces it to mevalonate, and statins block that step.

Rises when the methylation cycle stalls. A useful readout of folate, B12 and B6 status, and an independent cardiovascular risk marker.

The absorbed, reduced form of iodine. TPO oxidises it before attaching it to thyroglobulin.

The product of the rate-limiting step of cholesterol synthesis.

Noradrenaline. Made from dopamine, and converted onward to adrenaline in the adrenal medulla.

Condenses with acetyl-CoA to start each turn of the Krebs cycle.

The charged form of creatine. Hands its phosphate to ADP to regenerate ATP in the first seconds of hard effort.

The first steroid made from cholesterol. Everything downstream, cortisol, androgens and oestrogens, starts here.

Amino acid that gives collagen its kinked structure. Hydroxylating it needs vitamin C.

The end of glycolysis. Goes to acetyl-CoA when oxygen is available and to lactate when it is not.

Monoamine made from tryptophan. Mostly gut-resident, and the precursor of melatonin.

The large protein whose tyrosine residues thyroid hormone is assembled on and stored in.