Constitution and behavior of follicular structures in the human anterior pituitary gland

The follicular structures present in the human pituitary gland were studied, at the light-microscopic level, using histochemical and immunocytochemical techniques. The antisera applied in the peroxidase-antiperoxidase procedure were anti-hFSH beta, anti-hLH beta, anti-hPRL, anti-hGH, anti-hTSH beta, anti-hLPH beta, anti-pACTH, and anti-hACTH. In the 10 normal pituitaries examined, follicles were always found in the three areas of the adenohypophysis. The wall of the pars distalis follicles showed the seven immunoreactive cell types studied, while follicle-stimulating hormone (FSH) and luteinizing hormone (LH) cells were the only ones present in the wall of the pars tuberalis follicles. Most of the cell types studied were also present in the wall of the intermediate area follicles, but these follicles had characteristics not found in the other two areas. They were very large, with frequent interconnections forming a three-dimensional network of anastomotic cavities, and the colloid had different histochemical affinity. None of the hormones studied could be detected by immunocytochemistry within the follicular colloid. Three of the ten pituitary adenomas examined showed numerous follicular structures. Some of the follicles in the adenomatous pituitaries were similar to those found in the normal adenohypophysis, but there were also follicles filled with only traces of colloid and numerous blood cells in the cavity, and follicles filled with neoformed connective tissue. In one of these cases, FSH/LH immunoreactive adenoma cells were seen in the wall of the follicles. The results obtained suggest that the finding of pituitary adenomas with follicular structures is not uncommon and that the follicles originate from the tumor cells. In addition, the follicles seem to have several functional stages, explaining the finding of different types of follicular formation.