
influence of hormones on tumor growth and plasma prolactin levels in rats
bearing a pituitary "mammotropic" tumor
the effects of estradiol, cortisol acetate, thyroxine, or thiouracil on
tumor growth, organ weights, and plasma prolactin levels were determined
in rats bearing a furth pituitary "mammotropic" tumor (mtt.f4).  this
tumor is known to secrete large amounts of adrenocorticotropin, somatotropin,
and prolactin, but no follicle-stimulating hormone, luteinizing hormone,
or thyrotropin.  at the dose levels used, estradiol significantly suppressed
tumor growth without influencing body growth, and it partially inhibited
enlargement of the adrenals and atrophy of the thymus.  cortisol acetate
significantly reduced both tumor and body growth.  thyroxine had no significant
effect on tumor growth but enhanced the somatotropic effect as indicated by
increases in body growth and organ weights.  thiouracil had no significant
effect on tumor or body growth, although it significantly increased thyroid
weight.  estradiol, cortisol acetate, and thyroxine each increased the plasma
prolactin levels of the tumor-bearing rats.
