Cellular changes in the anterior pituitary of the domestic fowl during growth, sexual maturity and laying

All the cell types in the hen's anterior pituitary varied in number during the period from 10 weeks to adulthood; there was often an associated change in apparent functional activity. The cells most affected were the gonadotrophs (both FSH and LH) and luteotrophs; changes in these cells were associated with the onset and maintenance of sexual maturity. Follicle‐stimulating hormone cells were the first to increase in number and activity and this was correlated with a general increase in steroid output from the ovary, as measured by the oviduct weight increase. With the onset of follicular maturation LH cells became obvious. Prolactin cells increased in number with the presumed general increase in circulating oestrogen. Acidophilic somatotrophs decreased with increasing age; thyrotrophs became more numerous about sexual maturity and it is thought that this reflects the general increase in metabolic rate which occurs at this time.