[Insufficiency and excess of vitamin D activity (author's transl)]

The most important attainments acquired over the past ten years dealing with vitamin D action molecules, their intakes, photosynthesis, main effects, activation, transport, storage, inactivation, activity at the cellular levels are recalled. They are at the basis of the classification of the clinical states arising from either a deficiency or an excess of the vitamin D activity. Six mechanisms may explain the lack of activity : intake or cutaneous to solar exposure deficiency, lack of digestive absorption, liver metabolism disturbances, renal 1-hydroxylase failure, cellular receptors dysfunction, oncogenic rickets. Excess of activity result from intoxication with massive doses of vitamin D, their active metabolites or synthetized analogs ; it may also result from their hypersensitivity either idiopathic or related to sarcoidosis, thyroid as well as adrenocortical insufficiency. These data constitute an introduction to research concerning the role of vitamin D at skin level, in chondrocytes, bone cells and to a clinicopharmacological exposure.