Re-examination of the Discrepancy Between Acidophil Numbers and Growth Hormone Concentration in the Anterior Pituitary Gland Following Thyroidectomy

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Abstract
Differentlal cell counts of the anterior pituitaries from rats killed at intervals of from 4 to 18 days following thyroidectomy were compared with those of intact controls. At all intervals the reduction in acidophils correlated well with a rapid failure of growth. On the other hand, the growth hormone content of the anterior pituitary, as assayed In immature hypophysectomized rats by the tibia test, remained at normal levels until 18 days post thyroidectomy. A possible explanation for this discrepancy was that thyrotrophin, present in the extracts, augmented the assay. Reassay in hypophysectomized-thyroidectomized rats, which are remarkably sensitive to bovine growth hormone, revealed extremely low growth hormone concentrations at 12 days after thyroidectomy. The results suggest that contamination of pituitary extracts with thyrotrophin rather than an inability to observe acidophil granulation with the light microscope accounts for the failure to correlate growth hormone concentration with the status of the acidophils following thyroidectomy.