Hh

Initialism of Hedgehog; the gene and the signaling pathway are named after the protein.

Hh

1. (biology) A protein expressed in the larva of the fruit fly Drosophila melanogaster, required for the proper development of the larval body.
   1. The gene coding for the Hh (Hedgehog) protein.
   2. The signaling pathway involving the Hh (Hedgehog) protein, and its homologues in other animals.

From the two antigenic variants involved in the blood group system (the H and h antigens).

Hh

1. (medicine) A blood group system involving the presence of either the H or the h antigen on the surface of a person's red blood cells.