Hypothalamic‐hypophysial adrenal and thyroid systems: Observations in fetal rats subjected to hypothalamic destruction, brain compression and hypervitaminosis A

Fetal growth is regulated by fetal hormones in all species that have been studied. However, it is clear that strict definition of fetal growth must be applied in order that different studies and different species may be meaningfully compared. The experimental manipulation of fetal growth in vivo has been the main tool by which information in this area has been gained. Organ ablation experiments, with or without appropriate hormone replacement treatments, have been used now for nearly 50 years as a means of studying fetal growth. As the years have gone by, many of the original techniques have been refined beyond recognition, so that precise surgical or immunological approaches have now replaced the rather simpler earlier methods. However, the nature of the questions which are posed are still remarkably similar to those first formulated nearly 50 years ago. What regulates fetal growth? This article attempts to document the progress that has been made in the endocrine control of fetal growth.

Section: Fetal Pituitary and Fetal Growthmentioning

confidence: 88%

Endocrine Control of Fetal Growth

Browne

Thorburn

1989

“…It is also well known that the hypothalamo-pituitary-adrenal axis operates well dur ing the late period of fetal life [12,19,24,31]. Maternal administration of ACTH and corticoids causes regression of the fetal thy mus [3,10].…”

Section: Introductionmentioning

confidence: 99%

Influence of Adrenalectomy on the Development of the Neonatal Thymus in the Rat

Inomata

Nakamura²

1989

“…For example, the adrenal cortex is actively functioning at least a few days before birth [11,[13][14][15], regulated by the pituitary gland [10,16]. Also, there are some lines of evidence that the hypothalamus begins to control the pituitary-adrenal system before birth [5,10,11,16], though evidence indi cates that the onset of the hypothalamic con trol occurs slightly later than that of the pitu itary regulation of the adrenal [9], Adrenalectomy of pregnant rats results in a hypertrophy of the fetal adrenals near the end of gestation and just after birth [21], a phenomenon which is considered a compen satory event in the fetus owing to maternal adrenocortical deficiency. In relation to this, it will be pertinent to mention that maternal ACTH cannot cross the placenta [7], but cor ticoids can [1,6], Thus, the compensatory hypertrophy of fetal adrenals after maternal adrenalectomy is interpreted as a result of the negative feedback response of the fetal pitu itary-adrenal system to the declined amount of fetal circulating corticoids derived from the mother.…”

Section: Introductionmentioning

confidence: 99%

Developmental Changes in Fetal Adrenal Hypertrophy following Maternal Bilateral and Fetal Unilateral Adrenalectomy at Different Stages of Gestation in the Rat

Yamamoto¹,

Eguchi²,

Asari³

et al. 1983

Self Cite

Maternal adrenalectomy on days 14 and 15 of gestation did not alter the fetal adrenal weight 2 days later. The same operation on day 16 caused a significant increase in the adrenal weight with a hypertrophy of the cortical cells. Nevertheless, the operation on days 17 and 18 induced no change in the fetal adrenals. Subsequently on days 19 and 20, the operation resulted in a significant hypertrophy of the fetal adrenals. Fetal unilateral adrenalectomy on day 18 caused, 2 days later, significant hypertrophy of the contralateral adrenal, in contrast with no significant change after maternal adrenalectomy. This is perhaps due to the difference in the amount of fetal plasma corticoids, as evidenced by the previous reports of high concentrations of fetal plasma corticosterone on days 19 and 20. The overall results suggest that the fetal pituitary-adrenal feedback mechanism begins to appear between days 16 and 18 of gestation.