Adult male guppy; top: control, bottom: after exposure to 1.0 mg/L β-HCH for 3 months; PAS staining effect of β-hexachlorocyclohexane
(β-HCH) on the pituitary ¹

In the pituitary of male guppy exposed to β-hexachlorocyclohexane (β-HCH), the ventral part of the proximal pars distalis is enlarged (bottom), compared to the control specimen (top). This part contains gonadotropin producing cells, which are hypertrophied after exposure.
Note also the prominent staining of blood plasma within capillaries and of tissue fluid surrounding the pituitary in the exposed fish, indicative of high vitellogenin levels. The effects of β-HCH detected in this study were similar to those of estrogen, i.e. positive feedback on GTH cells in the pituitary and stimulation of vitellogenesis in the liver.