Post-partum dysthyroidism are not well understood by obstetricians, but are rather frequent (5.5% of the cases); they usually are the manifestation of a lympho-plasmocytic thyroidism with auto-immune origin. They are encouraged by a genetic predisposition and sometimes by food with a high iodine content. The disease starts with a phase of early thyreotoxicosis, 1 to 3 months following delivery, then later with hypothyroidism (from the 3rd to the 9th month), associated with menstrual disorders, an amenorrhea-galactorrhea syndrome or still, the occurrence of a goiter. Most of the time, the course is favorable, even in the absence of treatment with spontaneous return to euthyroidism within a few months, although the chance of permanent hypothyroidism is however non negligible. The diagnosis is difficult, and the treatment should be the least aggressive possible: beta-blocker during the thyreo-toxicosis phase, supplemental treatment during the hypothyroidism phase. There is a risk of recurrence during subsequent pregnancies.