Light‐microscopic examinations were performed in three groups of pigs: one sham‐operated control group, one group subjected to thyroidectomy (TX), and one group injected with parathormone (PTH) after thyroidectomy (TX + PTH). The kidneys of the sham‐operated animals were normal, whereas slight to moderate dilatation of some tubules was seen in the TX group. The most prominent changes in the TX + PTH group were calcium deposition, tubular dilatation and degeneration, inflammation, and hyperaemia. In addition there were hyaline casts, PAS‐positive globules and mitotic figures in the tubules. It is suggested that the calcium deposition caused by the PTH administration plays a major role in the development of degeneration in the tubular epithelium, and that these structural lesions are of importance in the development of reduced renal function.