The authors report 19 cases of non iatrogenic primary hypothyroidism in adults at Le Dantec Hospital of Dakar. Those cases had been found during a period of 6 years and half in the internal medicine service. The aim was to study clinical features, diagnosis and outcome of patients after treatment. The mean age of patients was 42.2 years with a sex-ratio of 0.33 M/F. The diagnosis delay was around 6,1 years. All patients presented clinical signs of hypometabolism: physical asthenia (63.15%), frilosity (26.3%), bradycardia (47.3%), constipation (36.8%). The cutaneomucal syndrom was composed by myxoedema (73.6%), macroglossia (26.3%), raucousness of voice (26.3%), alopecia (57.9%). Muscle weakness was found in 2 cases and genital troubles in 3 cases. Five patients presented goiter and 9 others had spontaneous thyroid atrophy. All patients presented a high level of TSH associated with decreased level of T4. Anemia was found in 7 cases and hypercholesterolemia in 13 cases. Treatment was based on substitutive hormonotherapy with L-Thyroxin (75 to 250 microg/day). Evolution was favorable after 10 month mean duration of processing. More alertness is necessary on behalf of the practitioners in front of any sign suggesting hypometabolism to reduce the diagnostic delay and prevent complete form of hypothyroidism that might be complicated, by cardiac involvement in particular.