Re-evaluation of the Effect of Estrogen on Thyroid Activity in the Rat and Its Mechanism

Yamada, Takashi; Takemura, Y; Kobayashi, Isao; Shichijo, K

doi:10.1210/endo-79-5-849

Cited by 24 publications

(6 citation statements)

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“…Two clinical reports show that clomiphene did not alter the PBI [9,35], There is disagreement about the PBI response in rats following estrogen injections. Results vary from no change [15,16,19] to reduced PBI values [38] in estrogen-treated or pregnant [17] rats. It is generally agreed that estrogen [21] or pregnancy [1] causes an elevation of PBI in the human by increasing thyroxin-binding protein (TBP).…”

Section: Discussionmentioning

confidence: 87%

“…Under circumstances where gonadotropin secretion is markedly increased, as after ovariectomy, the plasma and pituitary TSH titers are reduced [10,11]. In a brief report Labrie et al measured a rise in plasma TSH following a single estrogen in jection in the rat [24], Furthermore, serum TSH titers in the rat are highest during estrus, the time when estrogen levels are elevated [7,34], An in crease in thyroid weight following estrogen treatment is indirect evidence for an increase in TSH secretion [27,38]. The implantation of estradiol benzoate into the pituitary produces an increase in plasma TSH levels [12] suggesting that estrogen has a direct effect on the pituitary.…”

Section: Discussionmentioning

confidence: 99%

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Modification of Pituitary Thyrotropin and Thyroid Activity in the Rat Following Administration of Clomiphene Citrate

Gellert¹,

Bakke²,

Lawrence³

1970

Gynecol Obstet Invest

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Clomiphene citrate was administered to mature female rats at 5 dose levels for 16 days and pituitary thyrotropin levels were measured as well as indices of thyroidal and gonadal function. Thyroidal ¹³¹I uptake was increased, serum free thyroxin was reduced and PBI remained unchanged. A marked increase in pituitary TSH occurred. Estrous cycles were blocked and uterine weights reduced, however, no significant change was seen in ovarian weights except for reduction at the highest dose of clomiphene. Clomiphene depressed the usual thyroidal weight response to TSH when added to bovine thyroid slices invitro. The results suggests that clomiphene has direct effects on thyroidal iodide uptake and T₄ secretion, probably unrelated to direct central effects on pituitary TSH secretion.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Modification of Pituitary Thyrotropin and Thyroid Activity in the Rat Following Administration of Clomiphene Citrate

Gellert¹,

Bakke²,

Lawrence³

1970

Gynecol Obstet Invest

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“…Another previous study [20] has showed that circulating oestrogen could induce acute serum TSH suppression in males by acting on the pituitary gland, and vitamin D was shown to be an important factor in oestrogen biosynthesis of both female and male gonads [21]. However, oestrogen administration has been reported to both increase [22] and decrease [23] or have no effect on thyroid activity in females [24]. Therefore, it may be safely inferred that oestrogens have a complex relationship with serum TSH secretion in females, which may explain the cause of this relationship only in men.…”

Section: Discussionmentioning

confidence: 99%

Association of High Vitamin D Status with Low Circulating Thyroid-Stimulating Hormone Independent of Thyroid Hormone Levels in Middle-Aged and Elderly Males

Zhang

Wang

Sun

et al. 2014

International Journal of Endocrinology

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Background. A recent study has reported that high circulating 25-hydroxyvitamin D [25(OH)D] is associated with low circulating thyroid-stimulating hormone (TSH) levels, but only in younger individuals. The goal of the present study was to explore the relationship between vitamin D status and circulating TSH levels with thyroid autoimmunity and thyroid hormone levels taken into consideration in a population-based health survey of middle-aged and elderly individuals. Methods. A total of 1,424 Chinese adults, aged 41–78 years, were enrolled in this cross-sectional study. Serum levels of 25(OH)D, TSH, thyroid hormones, and thyroid autoantibodies were measured. Results. The prevalence of vitamin D insufficiency was 94.29% in males and 97.22% in females, and the prevalence of vitamin D deficiency was 55.61% in males and 69.64% in females. Vitamin D status was not associated with positive thyroid autoantibodies after controlling for age, gender, body mass index, and smoking status. Higher 25(OH)D levels were associated with lower TSH levels after controlling for age, FT4 and FT3 levels, thyroid volume, the presence of thyroid nodule(s), and smoking status in males. Conclusion. High vitamin D status in middle-aged and elderly males was associated with low circulating TSH levels independent of thyroid hormone levels.

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“…In experiment 4, beginning 10 days after surgical thyroidectomy, the animals were fed Remington low iodine diet plus either propylthiouracil (0.05%), methimazole (0.05%), sulfagua- nidine (1%) or methylthiouracil (0.05%), and injected with 4 jug of T 4 and 0.4 nc of 131 I-T 4 4 ip daily for 7 days. Twenty-four hr after the injection of T 4 , blood was obtained by cardiac puncture and the PBI of the serum was determined by both chemical 3 and isotopic techniques (16).…”

Section: Methodsmentioning

confidence: 99%

An Essential Role of Thyroxine and Triiodothyronine Balance in Establishing Normal Pituitary-Thyroid Feedback Control in Goitrogen-Treated Rats

Yamada

Lewis

1968

Endocrinology

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Rats were fed propylthiouracil (0.05 %), methimazole (0.05 %), or sulfaguanidine (1 %) and injected with graded doses of thyroxine (0.5-3.0 jug) daily for 2 weeks. In spite of the high serum PBI with doses of 1.0 and 1.5 jug of thyroxine, goiter was still observed in animals fed propylthiouracil. Goiter was prevented only when the PBI was increased to 2.2 times that of the control level by giving 2.0 jug of thyroxine. Similar effects were found with methimazole and sulfaguanidine. In animals which were thyroidectomized and given thyroxine, methimazole slightly elevated the serum PBI and reduced the urinary excretion of radioiodine after a single injection of labeled thyroxine. However, since sulfaguanidine was without effect in these respects, the development of goiter in the presence of a high serum PBI cannot be explained by assuming that all 3 goitrogens interfered with the deiodination of thyx'oxine. On the other hand, goiter was prevented in propylthiouracil-fed animals by doses of thyroid powder which resulted in a serum PBI lower than normal. Furthermore, goiter prevention in methimazolefed animals was achieved by administering a mixture of triiodothyronine (0.1 jug) and thyroxine (1.0 /xg) which produced a normal serum PBI and thyrotropin level. Since normally triiodothyronine plays an important physiologic role, it is suggested that goiter could not be prevented without giving a dose of thyroxine that would elevate the serum PBI to compensate for the activity of triiodothyronine. The existence of a homeostatic relation between the level of serum PBI and thyrotropin secretion by the anterior pituitary can be shown in goitrogentreated animals only when an appropriate mixture of triiodothyronine and thyroxine is administered. (Endocrinology 82: 91, 1968) AS FIRST formulated by Aron et al.(1) J\. and then reiterated by Hoskins (2), it is generally held that the pituitarythyroid axis offers an example of a physiologic servomechanism. When the titer of circulating thyroxine rises, the anterior pituitary is selectively inhibited, and thereby the output of thyrotropin falls. On the other hand, episodic or persistent decrease of circulating thyroxine results in an increased secretion of thyrotropin. Since probably over 90% of the iodine in blood is represented by thyroxine (3-5), it has been suggested that the level of thyroxine, measured as PBI, may regulate the secretion of thyrotropin. Although most

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Re-evaluation of the Effect of Estrogen on Thyroid Activity in the Rat and Its Mechanism

Cited by 24 publications

References 1 publication

Modification of Pituitary Thyrotropin and Thyroid Activity in the Rat Following Administration of Clomiphene Citrate

Modification of Pituitary Thyrotropin and Thyroid Activity in the Rat Following Administration of Clomiphene Citrate

Association of High Vitamin D Status with Low Circulating Thyroid-Stimulating Hormone Independent of Thyroid Hormone Levels in Middle-Aged and Elderly Males

An Essential Role of Thyroxine and Triiodothyronine Balance in Establishing Normal Pituitary-Thyroid Feedback Control in Goitrogen-Treated Rats

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