Pregnancy and the Thyroid Gland

Abstract

The relation of thyroid activity to sex and its functions has long been recognized, but the particulars of this relationship have been subjects of endless speculation and conflicting hypotheses. Before presenting the few additional facts we have to offer, it may be well to review the facts already available and current opinions on the subject. Women are undoubtedly more susceptible than are men to all recognized functional disturbances of the thyroid gland, especially hyperactivity of the organ. The incidence of this latter condition appears to be greater during periods of changing sexual function-adolescence and the menopause. Concerning the effect of pregnancy there is some difference of opinion. It is generally agreed that the thyroid gland undergoes hyperplasia during pregnancy, but there is no certainty that this hyperplasia is attended by hyperfunction. The basal metabolism rises in the latter months of pregnancy,8, 10, 19, 21 but the rate of oxidation is not controlled by the thyroid gland alone. The rise of basal metabolism in pregnancy is not accompanied by other recognized manifestations of hyperthyroidism. Indeed, serum cholesterol is said to increase, a phenomenon that is regularly observed in hypothyroidism.1'4'8 The hypermetabolism of pregnancy is not regularly accompanied by the circulatory or nervous manifestations that characterize hyperthyroidism.Clinical hyperthyroidism may begin during pregnancy, but this does not seem to be a frequent occurrence.10 Clinical hyperthyroidism does not appear to influence the normal course of pregnancy nor to prevent conception. Thyroidectomized female animals are unable to conceive. Complete absence of the gland produces sterility in both sexes. This has given rise to the impression that infertility in women with normal menses may be due to some lesser degree of thyroid deficiency. Convincing evidence for such a concept has been hard to find, chiefly be-

Endocrinopathies et grossesse

“…Peters et coll. ont montré que les valeurs habituelles du PBI comprises entre 4 et 8pg/10Uml croissaient dès le second mois de la grossesse pour atteindre à terme 6,2 à 1 1,2 uni/100 ml (65). Le métabolisme basal est aussi plus élevé d'environ 20 % au cours du dernier trimestre de la grossesse et retrouve des valeurs normales vers la fin de la première semaine du post-partum.…”

Emotional Factors in the Etiology of Hyperthyroidism Occurring in Relation to Pregnancy

“…and remain at these levels throughout gestation. 3 ' G - 14 The thyroid frequently enlarges and the basal oxygen consumption increases about 30 per cent during the last trimester. As not more than half this rise can be attributed to the high metabolic rate of fetal tissues, it seems likely that the alteration in thyroid activity occurs in response to hormonal changes accompanying pregnancy and is needed to promote fetal growth.…”

Endocrine Review: THE CLINICAL SIGNIFICANCE OF THE BLOOD IODINE: A REVIEW*

“…Danowski reported a trend toward a midcycle rise in the PBI, with a decrease during the postovulatory phase (134). Peters et al have shown a small decrease in the PBI from premenstrual to postmenstrual states (135). At least one investigator could determine no fluctuation in the blood iodine during the menstrual cycle (136).…”