In familial hypercholesterolemia, individuals homozygous for the allele causing the disorder completely lack receptors on liver cells that take up cholesterol from the bloodstream. Heterozygotes have one-half the number of receptors while individuals homozygous for the normal allele are phenotypically normal. This is an example of

Therapeutic drugs can be preventative or reactionary and bring relief, respite, and sometimes healing and recovery for a number of ailments. Therapeutic drugs can be over-the-counter or prescribed, taken as needed or regularly.

They are sometimes regulated by the government or monitored closely by health professionals.