The influence of hyperthyroidism on the hypothalamic-pituitary-gonadal axis

Zähringer, S.; Tomova, Analia; Werder, K. Von; Brabant, Georg; Kumanov, Philip; Schopohl, Jochen

doi:10.1055/s-2000-7756

Cited by 40 publications

(24 citation statements)

References 23 publications

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“…In cardiomyocytes, sex hormone receptors influence the activity of cardiac Na C /K C ATPase. In hyperthyroid men, impaired sexual function, gynecomastia, asthenospermia, and low testicular volume are attributed to lowered bioavailable testosterone and a decreased free androgen index despite an increase in total and SHBG-bound testosterone (Abalovich et al 1999, Zahringer et al 2000. The decreased bioavailable testosterone level in hyperthyroid men results in less shortening of the QTc interval.…”

Section: Discussionmentioning

confidence: 99%

High free thyroxine levels are associated with QTc prolongation in males

Noord¹,

Deure²,

Sturkenboom³

et al. 2008

Journal of Endocrinology

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The literature on the effect of excess thyroid hormone on ventricular repolarization is controversial. To study whether free thyroxine (T 4 ) and TSH are associated with QTc prolongation we conducted population-based cohort study. This study was conducted as part of the Rotterdam Study and included 365 men and 574 women aged 55 years and older with an electrocardiogram, who were randomly sampled for the assessment of thyroid status (free T 4 /TSH) at baseline, after exclusion of participants with hypothyroidism, use of antithyroid drugs, thyroid hormones or digoxin, left ventricular hypertrophy, and left and right bundle branch block. Endpoints were the length of the QTc interval and risk of borderline QTc prolongation. The associations were examined by means of linear and logistic regression analysis, adjusted for age and gender, diabetes mellitus, myocardial infarction, hypertension, and heart failure. Overall, there was no significant association between TSH and QTc interval (0 . 8 ms (95% confidence interval (CI) K3 . 5, 5 . 2) in the first quintile compared with the fifth quintile). Subjects in the fifth quintile of free T 4 did not have an increased QTc interval (3 . 2 ms (95% CI K1 . 1, 7 . 6)); stratification on gender showed an increment of 10 . 9 ms (95% CI 3 . 4, 18 . 3) in the fifth quintile in men and 1 . 1 ms (95% CI K4 . 2, 6 . 3) in the fifth quintile of free T 4 in women. When compared with subjects in the first quintile, male subjects in the fifth quintile of free T 4 had a significantly increased risk of a borderline QTc interval and QTc prolongation (odds ratio 2 . 40 (95% CI 1 . 20, 4 . 80)). High levels of free T 4 are associated with substantial QTc prolongation in men of up to 10 ms. The fact that free T 4 is also associated with a significantly increased risk of borderline and prolonged QTc values with its risk of sudden cardiac death, endorses the clinical importance of our findings.

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Section: Discussionmentioning

confidence: 99%

High free thyroxine levels are associated with QTc prolongation in males

Noord¹,

Deure²,

Sturkenboom³

et al. 2008

Journal of Endocrinology

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“…Several studies have shown that altered thyroid status has remarkable effects on Leydig cell differentiation in experimental animals dism, pituitary hyperplasia may occur causing multiple pituitary hormone deficiencies, including gonadotropin and corticotropin deficiencies (45). Low T3, high TSH and hyperprolactinemia caused by hypothyroidism could directly act on the Leydig cells in suppressing steroidogenesis (42,43,46). All the above changes are fully reversible with restoration of euthyroid state (12).…”

Section: Thyroid Hormone and Testicular Functionmentioning

confidence: 98%

Clinical implications of altered thyroid status in male testicular function

Wajner

Wagner

Maia

2009

Arq Bras Endocrinol Metab

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Thyroid hormones are involved in the development and maintenance of virtually all tissues. Although for many years the testis was thought to be a thyroid-hormone unresponsive organ, studies of the last decades have demonstrated that thyroid dysfunction is associated not only with abnormalities in morphology and function of testes, but also with decreased fertility and alterations of sexual activity in men. Nowadays, the participation of triiodothyronine (T3) in the control of Sertoli and Leydig cell proliferation, testicular maturation, and steroidogenesis is widely accepted, as well as the presence of thyroid hormone transporters and receptors in testicular cells throughout the development process and in adulthood. But even with data suggesting that T3 may act directly on these cells to bring about its effects, there is still controversy regarding the impact of thyroid diseases on human spermatogenesis and fertility, which can be in part due to the lack of well-controlled clinical studies. The current review aims at presenting an updated picture of recent clinical data about the role of thyroid hormones in male gonadal function. RESUMOOs hormônios da tireoide estão envolvidos virtualmente no desenvolvimento e na manutenção de todos os tecidos. As gônadas masculinas foram, por décadas, consideradas insensíveis aos hormônios tireoidianos. No entanto, estudos mais recentes têm demonstrado que disfunções tireoidianas estão associadas não somente a anormalidades na morfologia e na função dos testículos, mas também à diminuição da fertilidade e alterações na atividade sexual masculina. Atualmente, o papel da triiodotironina (T3) no controle da proliferação das células de Sertoli e Leydig, maturação testicular e esteroidogênese é amplamente aceito, bem como a presença de transportadores e receptores para o hormônio tireoidiano nos testículos durante o período de desenvolvimento e a idade adulta. No entanto, apesar dos dados que indicam que o T3 atua diretamente nos testículos humanos, persistem controvérsias em relação ao impacto das doenças tireoidianas sobre a espermatogênese e a fertilidade, o que pode ser em parte devido à escassez de estudos clínicos nessa área. Essa revisão tem por objetivo apresentar um panorama de dados clínicos atualizados sobre o papel dos hormônios tireoidianos na função gonadal masculina. Arq Bras Endocrinol Metab. 2009;53(8):976-82 Descritores

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“…Pontikides et al (134) found similar results when they studied women in the middle of the luteal phase of the cycle. Zä hringer et al (42) studied seven women with GD and six controls, sampling blood every 10 min for an 8-h period in the early follicular phase of the menstrual cycle. The authors found that LH secretion was increased, whereas the pulsatile characteristics of LH and FSH secretion did not differ in patients when compared with controls.…”

Section: A Thyrotoxicosis In Femalesmentioning

confidence: 99%

Thyroid Function and Human Reproductive Health

Krassas¹,

2010

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Via its interaction in several pathways, normal thyroid function is important to maintain normal reproduction. In both genders, changes in SHBG and sex steroids are a consistent feature associated with hyper- and hypothyroidism and were already reported many years ago. Male reproduction is adversely affected by both thyrotoxicosis and hypothyroidism. Erectile abnormalities have been reported. Thyrotoxicosis induces abnormalities in sperm motility, whereas hypothyroidism is associated with abnormalities in sperm morphology; the latter normalize when euthyroidism is reached. In females, thyrotoxicosis and hypothyroidism can cause menstrual disturbances. Thyrotoxicosis is associated mainly with hypomenorrhea and polymenorrhea, whereas hypothyroidism is associated mainly with oligomenorrhea. Thyroid dysfunction has also been linked to reduced fertility. Controlled ovarian hyperstimulation leads to important increases in estradiol, which in turn may have an adverse effect on thyroid hormones and TSH. When autoimmune thyroid disease is present, the impact of controlled ovarian hyperstimulation may become more severe, depending on preexisting thyroid abnormalities. Autoimmune thyroid disease is present in 5-20% of unselected pregnant women. Isolated hypothyroxinemia has been described in approximately 2% of pregnancies, without serum TSH elevation and in the absence of thyroid autoantibodies. Overt hypothyroidism has been associated with increased rates of spontaneous abortion, premature delivery and/or low birth weight, fetal distress in labor, and perhaps gestation-induced hypertension and placental abruption. The links between such obstetrical complications and subclinical hypothyroidism are less evident. Thyrotoxicosis during pregnancy is due to Graves' disease and gestational transient thyrotoxicosis. All antithyroid drugs cross the placenta and may potentially affect fetal thyroid function.

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The influence of hyperthyroidism on the hypothalamic-pituitary-gonadal axis

Cited by 40 publications

References 23 publications

High free thyroxine levels are associated with QTc prolongation in males

High free thyroxine levels are associated with QTc prolongation in males

Clinical implications of altered thyroid status in male testicular function

Thyroid Function and Human Reproductive Health

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