SUMMARY

Hypogonadal (hpg) mice lack hypothalamic luteinizing hormone releasing hormone (LH\x=req-\ RH). Gonadotrophs from male hpg mice have been identified by immunocytochemistry for LH and quantitative electron microscopy allied with radioimmunoassay of the gonado-trophins. In comparison with those of normal mice, gonadotrophs in male hpg animals are less numerous and smaller, with less cytoplasm and rough endoplasmic reticulum and a smaller Golgi apparatus. They have fewer granules, especially those of larger (> 210 nm) diameter. Thus, in the absence of LH-RH, gonadotrophs can differentiate but remain relatively inactive