This group comprises all hormonal preparations for systemic use, except:
- Insulins, see A10.
- Anabolic steroids, see A14.
- Catecholamines, see C01C and R03C.
- Sex hormones, see G03.
- Sex hormones used in treatment of neoplastic diseases, see L02.
- Metreleptin used for treatment of complications of leptin deficiency in patients with generalised lipodystrophy is classified in A16AA.

Iodine-therapy products that influence hormonal synthesis or function are classified in H03C - Iodine therapy.

This group comprises thyroid extracts and synthetic analogues used in the treatment of hypothyrosis.

This group comprises natural and synthetic thyroid hormones. Combinations of levothyroxine and liothyronine are classified at a separate 5th level: H03AA03.
Liothyronine hydrochloride is classified in H03AA02.