Geelhoed G W
Chirurgie. 1990;116(6-7):501-8.
An old bull, it is said by those who know, can have his troubles. Included among these are vertebral osteosclerosis and ankylosing spondylosis--this stiffening up limite, rather than accentuates, the value and reproduction potential of a stud bull past prime. But associated with these abnormalities--and not seen in age-matched cows of comparable breeds--are fascinating endocrine neoplasms that might suggest a pattern that could be productive as a model of human hereditary endocrine abnormalities. Adjacent to the thyroid gland in other vertebrates are ultimobranchial bodies, that are incorporated into the lateral thyroid lobes in primates as the parafollicular "C-cells" of the thyroid. These are the cells in man that give rise to medullary thyroid cancer and are associated with calcitonin secretion, useful as a tumor marker. In aging bulls of whatever breed, nearly half exhibit abnormality of these ultimobranchial bodies: 20% show hyperplasia, and 30% have frank neoplasia. These ultimobranchial tumors appear in bulls passing 6 1/2 years in age, and are absent in young bulls and all cows of any age. Calcitonin can be demonstrated in the ultimobranchial tumors from bulls, and secretion is stimulated by calcium infusion, though serum calcium remains normal. The ultimobranchial tumors themselves can range from hyperplasia through adenoma to metastasizing carcinoma--in fact, representing one of the commoner cattle cancers. Parathyroid glands taken from bulls with these ultimobranchial tumors initially show evidence of inhibited secretory activity and morphologic atrophy, but later go on to develop hyperplasia and, eventually, autonomy.(ABSTRACT TRUNCATED AT 250 WORDS)
据说，上了年纪的公牛会有不少麻烦。其中包括脊椎骨硬化和强直性脊柱炎——这种身体僵硬不仅不会增强，反而会限制壮年种公牛的价值和繁殖潜力。但与这些异常情况相关联的——在年龄匹配的同品种母牛中未发现——是一些引人入胜的内分泌肿瘤，这可能暗示着一种模式，有望成为人类遗传性内分泌异常的模型。在其他脊椎动物中，甲状腺旁有后鳃体，在灵长类动物中，后鳃体并入甲状腺侧叶，成为甲状腺的滤泡旁“C细胞”。人类的这些细胞会引发甲状腺髓样癌，并与降钙素分泌有关，降钙素可用作肿瘤标志物。无论何种品种的老龄公牛，近半数都表现出这些后鳃体异常：20%表现为增生，30%有明显的肿瘤形成。这些后鳃体肿瘤出现在6岁半以上的公牛身上，幼龄公牛和所有年龄段的母牛均未出现。在公牛的后鳃体肿瘤中可检测到降钙素，静脉注射钙可刺激其分泌，不过血清钙仍保持正常。后鳃体肿瘤本身的范围从增生到腺瘤，再到转移性癌——实际上，它是牛类较常见的癌症之一。从患有这些后鳃体肿瘤的公牛身上取出的甲状旁腺，最初显示出分泌活动受抑制和形态萎缩的迹象，但随后会发展为增生，最终出现自主性。（摘要截选至250词）
