Pituitary and Associated Hormone Factors in Cranial Growth and Differentiation in the White Rat: A Roentgenological Study

Abstract

IN man, in a large proportion of cases in which the cranial skiagram gives evidence of cranial dysplasia, there is found, clinically, evidence of past or present disturbance of pituitary function either during the growth period, subsequent to it, or throughout life. Such disturbance, whether it be on the side of hyperfunction, hypofunction, or a period of the former followed by a phase of the latter, we shall describe under the general heading “Pituitary Dysfunction.” By cranial dysplasia we mean such abnormality in form or structure that the skull can be regarded as “malformed,” the degree of this being subject to wide variation, ranging from a proportion and structure which cannot be regarded as outside the zone of supposedly normal variation, to gross deformity. Thus, the skull may be proportionate in its component parts and structure, the abnormality lying in its being too large or too small for the sex and age of the patient; the facial component may be disproportionate to the size of the brain-case through overgrowth or underdevelopment of either the former or latter; the component parts of the face, respiratory and masticatory, may be disproportionate one to the other, from overgrowth or underdevelopment of either. There may be such a calvarial contour as is abnormal for the sex or age or even for the stock to which the individual belongs. The brain-case may be abnormal in thickness or density, or its normal architectural structure, of three tables, may be lost to a lesser or greater degree. Clinically, from such a correlation between cranial dysplasia and pituitary dysfunction, a causal relationship may be presumed between them; nevertheless, the need is felt of experimental evidence to demonstrate the influence of pituitary hormones on cranial size, form, and structure. For this reason it was decided to examine roentgenologically the crania of rats treated with various relatively highly purified pituitary hormone-fractions. Against the disadvantage of the fact that the rat cranium has not been the subject of any extensive study by craniologists may be set several distinct advantages; the rat of the Wistar stock is stable morphologically, it is in wide use for experimental purposes, its skull in many ways shows a pattern of growth not unlike the human, and there is a well marked difference to be seen in size and proportions between the male and female crania. But the chief advantage lies in the fact that the same animals, studied radiographically, have been investigated physiologically by a number of workers whose findings are available for confirmation or control of x-ray findings; especially is this true of animals that have been the object of calcium metabolism studies and in which the daily output of calcium, and the balance, is known over relatively long periods.