This study aims to evaluate the effects of castration and iodine supplementaion on the histological structure of pituitary and thyroid glands and their related hormones in NZW male rabbits. Animals were randomly divided into two groups. The first group was supplemented with iodine as potassium iodide at a level of 400 ppm, while the other was control. Each group was divided into two subgroups; the first subgroup was bilaterally castrated (BC) after testicles descended using banding technique, while the other served as an intact (INT) control. Plasma luteinizing hormone (LH) concentrations were increased (P<0.01) in BC compared to INT rabbits, with or without iodine supplementation. Plasma T3 and T4 levels were lower (P<0.01) in BC than in INT rabbits, while they were higher (P<0.01) with iodine in BC rabbits than in INT ones. Histological changes observed in the pituitary were as follows : Castration alone induced an increase in basophil number and a reduction in the number of acidophils and chromophobe cells. Many of these cells in BC rabbits had a ring of clear cytoplasm around their nuclei and their pituitaries showed increased vascularisation. In INT rabbits with iodine, basophility increased, showing presence of polygonal hypertrophied basophils. In BC rabbits with iodine, the number of basophils of large-sized was greatly increased. Histological alterations in the thyroid were as follows : In BC rabbits, there was a remarkable increase in fibroblasts. Follicular cells appeared less closely packed to each other and their epithelium was cuboidal. The number of parafollicular cells, however, did not change in BC sections. The colloid appeared less homogenous in BC than in INT sections. In INT rabbits with iodine, there was a marked change in follicular cell shape, which was converted to squamous epithelium. They have a marked depletion in parafollicular cells and colloid substance. In BC rabbits with iodine, the follicular epithelium was flattened, resembling that of the INT with iodine, and there was a severe depletion in parafollicular cells and colloid.
KEY WORDS: castration, iodine, pituitary and thyroid hormones, histology, rabbits
Egyptian Journal of Biology Vol.3(2) 2001:38-47