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Plerocercoid larvae of the tapeworm, Spirometra mansonoides produce a growth hormone-like factor that stimulates body growth of a variety of normal and hormone-deficient animals. Plerocercoid infection (15 per hamster) stimulated an increase in body weight, and markedly suppressed pituitary weight and growth hormone (GH) concentrations of serum and pituitaries of Syrian hamsters. The suppression of serum GH persisted for at least 4 mo after the initiation of infection. The presence of plerocercoids also resulted in a significant reduction (30-50%) in serum thyroxine (T4). The pronounced lipogenic effect associated with plero- cercoid infection was not reversed by injection of the infected hamsters with high (10 or 20 jig/day) or low (1 or 2 jg/day) doses of L-thyroxine. These results suggest that the plerocercoid growth factor may function in a manner similar to high levels of endogenous GH by activating the feedback system that inhibits pituitary secretion of both GH and TSH. Whereas hypothyroidism may be associated with hyperlipidemia the resultant hypothyroid state induced by plerocercoid infection does not explain the hypertriglyceridemia and hypercholesterolemia which were a consistent observation in plerocercoid-infected hamsters. Plerocercoid larvae of the tapeworm, Spiro- metra mansonoides produce a growth hormone (GH)-like factor that stimulates body growth of a variety of normal and hormonally deficient rodents (Mueller, 1974). The presence of plero- cercoids in intact rats results in a dramatic reduc- tion in pituitary weight and circulating levels of GH (Garland et al., 1971; Glitzer and Steelman, 1971). Therefore, most of the effects of plero- cercoid growth factor (PGF) are similar to those of GH. Lipid metabolism is a notable exception. Chronic administration of GH results in a |
