384 NELSON W. JANNEY 



Age. ^No age is exempt from the disease. Congenital thyreoaplastic 

 cases develop cretin symptoms shortly after birth. Older children seem 

 more frequently affected in the sixth to the eighth year. At puberty there 

 is an increased incidence, particularly in females. According to Dock (c), 

 myxedema gradually increases in frequency up to the forty-fifth year, 

 then decreases, the average age in woman being thirty-eight years, in men 

 forty-two. The earlier age of onset in women is probably related to the 

 increased strain put upon the thyroid by gestation. In general, it may 

 be said that the most active periods of growth of the individual or the 

 embryo are of chief importance in determining the favorite age of inci- 

 dence; thus illustrating the importance of the thyroid gland in such vital 

 processes. 



Sex. The female sex is predominately affected in childhood according 

 to Hector MacKenzie (a), who collected 292 cases of cretinism from the lit- 

 erature of whom 172 or 60 per cent were females. After puberty the pro- 

 portion of affected females is much greater, 4:1 (Biedl), 7:1 (Dock (c)). 



In some instances gestation seems to exert a protecting influence 

 against the outbreak of hypothyroidism in predisposed individuals, 

 through a general endocrin stimulus and resulting thyroid hyperplasia. 

 The disease then develops about the menopause. On the other hand, 

 pregnancy may add an overload on a subfunctionating thyroid gland with 

 resulting symptoms of hypothyroidism. Virgins are by no means exempt 

 from hypothyroidism, however. In a case of the writer's series an elderly 

 hypothyroid primipara, who previous to her pregnancy maintained a 

 normal metabolic rate on 0.4 mgm. thyroxin daily, became again hypo- 

 thyroid during the later months of gestation, the basal metabolism falling 

 to 20. On increasing the daily dose of thyroxin to 0.8 mgm., the sub- 

 thyroidism subsided and the metabolic rate rose to normal. 



Environment. The causal relationship of unsanitary surroundings 

 to the development of goiter and endemic cretinism has long been recog- 

 nized. It may, therefore, be expected that sporadic hypothyroidism arises 

 from similar momenta. Clinically, sporadic cretinism is seemingly met 

 with more frequently among the lower orders of society, where probably 

 a combination of etiological factors such as overwork on improper or 

 defective food supply, therefore general nutrition, alcohol, neglected infec- 

 tions, abnormal sexual activity and many pregnancies predispose to hypo- 

 thyroidism in the offspring. 



Infectious Origin. Major K. McCarrison of the Indian Medical 

 Service has made very valuable experimental contributions on the etiology 

 of goiter and cretinism (see his monograph, bibliography). As his 

 results in these regards are especially pertinent to the Cretinic Degenera- 

 tion they will here be merely alluded to. McCarrison firmly adheres to the 

 infectious origin of goiter and cretinism in both their sporadic and en- 

 demic expressions, believing them frequently due to an infectious intestinal 



