Hormones and Water and Electrolyte Metabolism 81 



possible significance occur. Thus, a considerable growth 

 spurt in the weight of the adrenal gland, more in boys than 

 in girls, has been observed. It is almost entirely due to growth 

 of the cortex. The weight of the thyroid also shows an adoles- 

 cent spurt, but without any sex difTerence. Scanty data on 

 hormone excretion indicate a slow increase in the excretion 

 of oestrogen in both boys and girls during childhood, with a 

 marked increase at puberty in the case of girls, while in boys 

 the rate of increase hitherto manifested is merely maintained. 

 Androgen excretion is similar in the two sexes before puberty ; 

 after puberty there is a marked rise in the case of boys, but a 

 not unimportant rise also occurs in girls, no doubt as a result 

 of increased adrenocortical activity. There is a gradual rise in 

 the rate of secretion of adrenal corticoids, without sex dif- 

 ference, from birth to maturity. The increase appears to be 

 proportionate to body size, without any adolescent spurt. 

 The blood level of 17-hydroxy corticosteroids is much the 

 same at all ages, and the responsiveness of the adrenals to 

 stimulation by adrenocorticotrophic hormone is also un- 

 affected by age, except, of course, in so far as the adrenal 

 glands are smaller in children than in adults. A steady fall 

 in the serum protein-bound iodine over the years six to 15 

 parallels the fall in basal metabolic rate, and the precise 

 significance of this is obscure. 



The sum total of these changes does not seem to have any 

 striking impact on fluid and electrolyte metabolism. 



Effects of the Menstrual Cycle 



An important sex difference is introduced by the cyclic 

 variations in hypothalamic-pituitary-ovarian (and perhaps 

 adrenocortical) function which determine the menstrual 

 cycle in females. It might well be expected that these 

 would lead to important fluctuations in fluid and electrolyte 

 balance. 



Variations in body fluid during the menstrual cycle have 

 been recognized for a long time, but the first full description 

 of "premenstrual oedema" was given by Thomas (1933) who 



