Effect of hypothyroidism on the hypothalamic-pituitary-ovarian axis and reproductive function of pregnant rats

The effects and toxicological mechanisms of leucaena toxicity on ruminant reproduction: a review

Leucaena leucocephala (leucaena) is a high-quality proteinaceous feed which can improve the nutrition of ruminant livestock in tropical countries. However, this legume contains toxic secondary compounds (mimosine and dihydroxypyridine) in all parts of the plant. Several studies have shown that leucaena secondary compounds could damage male and female animals' reproductive performance, including decreased libido and semen quality, embryonic and foetal death, malformation, and lower the conception rate. This paper identifies some toxicological mechanisms that might be responsible for reproductive failure in the ruminant. Some strategies are suggested to make leucaena feeding safer for breeding ruminants. These can be categorised into strategies that reduce the toxicity of mimosine and DHP via detoxification pathways, and strategies that counteract certain effects of toxicity, and so indirectly reduce the impact on reproductive function.

Mild Gestational Hypothyroidism in Mice Has Transient Developmental Effects and Long-Term Consequences on Neuroendocrine Systems

Background: Thyroid hormones (TH) play a key role in fetal brain development. While severe thyroid dysfunction, has been shown to cause neurodevelopmental and reproductive disorders, the rising levels of TH-disruptors in the environment in the past few decades have increased the need to assess effects of subclinical (mild) TH insufficiency during gestation. Since embryos do not produce their own TH before mid-gestation, early development processes rely on maternal production. Notably, the reproductive network governed by gonadotropin-releasing hormone (GnRH) neurons develops during this critical period. Methods: The risk of mild maternal hypothyroidism on the development of GnRH neurons and long-term effect on neuroendocrine function in the offspring was investigated using a mouse model of gestational hypothyroidism induced by methimazole (MMI) treatment. Results: MMI treatment during gestation led to reduced litter size, consistent with increased miscarriages due to hypothyroidism. E12/13 embryos, collected from MMI-treated dams, had a decreased number of GnRH neurons, but the migration of the remaining GnRH neurons was normal. Cell proliferation was reduced in the vomeronasal organ (VNO), correlating with the reduced number of GnRH neurons detected in this region. Using a GnRH cell line confirmed attenuated proliferation in the absence of T3. Pups born from hypothyroid mothers had normal postweaning growth and estrus cycles, yet adult offspring had significantly more cells expressing estrogen receptor alpha in the arcuate nucleus. Notably, by adulthood, GnRH cell number and distribution was comparable with nontreated controls indicating that compensatory mechanisms occurred after E13. Conclusion: Overall, our work shows that mild TH disruption during gestation transiently affects proliferation of the pool of GnRH neurons within the VNO and has a long-term impact on neuroendocrine systems.

Advancing thyroid disease research: The role and potential of zebrafish model

Thyroid disorders significantly affect human metabolism, cardiovascular function, skeletal health, and reproductive systems, presenting a complex challenge due to their multifactorial nature. Understanding the underlying mechanisms and developing novel therapeutic approaches require appropriate models. Zebrafish, with their genetic tractability, short life cycle, and physiological relevance, have emerged as a valuable model for investigating thyroid diseases. This review provides a comprehensive analysis of the zebrafish thyroid gland's structure and function, explores its application in modeling thyroid pathologies such as hypothyroidism, hyperthyroidism, and thyroid cancer, and discusses current limitations and possible improvements. Furthermore, it outlines future directions for zebrafish-based research, focusing on enhancing the model's relevance to human thyroid disease and its potential to expedite the development of clinical therapies.

Artemisinin ameliorates thyroid function and complications in adult male hypothyroid rats via upregulation of the L1 cell adhesion molecule

BACKGROUND

Hypothyroidism, a common worldwide syndrome caused by insufficient thyroid hormone secretion, affects number of people at different ages. Artemisinin (ART), a well-known effective agent in the treatment of malaria, also has anti-oxidative stress functions in various diseases. The L1 cell adhesion molecule exerts multiple protective roles in diseased systems. The aim of the present study was to evaluate the role of ART in adult male hypothyroid rats and the underlying mechanisms.

METHODS

The propylthiouracil (PTU) rat model was treated with or without 5 mg/kg ART and with or without L1 short-interfering RNA (siRNA), followed by the experiments to determine the effect of ART on thyroid function, depression and anxiety, cognition impairments, liver, kidney and heart functions, and oxidative stress.

RESULTS

In the current study, it was shown that ART can ameliorate thyroid function, mitigate depression and anxiety symptoms, attenuate cognition impairments, improve liver, kidney and heart functions, and inhibit oxidative stress; however, the effects exerted by ART could not be observed when L1 was silenced by L1 siRNA.

CONCLUSION

These results indicated that ART can upregulate the L1 cell adhesion molecule to ameliorate thyroid function and the complications in adult male hypothyroid rats, laying the foundation for ART to be a novel strategy for the treatment of hypothyroidism.

The common pathogenesis of nodular goiter in both sexes: An exploration into gene expression and signaling pathways

The past few years have witnessed an increasing incidence of nodular goiter (NG), with a well-documented higher prevalence in females than males. This gender disparity has led research to focus primarily on female subjects, potentially overlooking common pathogenic mechanisms in both sexes. In this study, we investigated the shared pathogenesis of NG in males and females. Utilizing a rat model and RNA sequencing, we identified differentially expressed genes associated with the disease. We further validated these findings in normal human thyroid cells and human papillary thyroid cancer cells. A randomized experiment was conducted with equal numbers of male and female rats divided into control and NG model groups. The NG model was established using propylthiouracil and various assessments such as thyroid ultrasonography, thyroid index, thyroid function, and thyroid histology were performed. Transcriptome analysis revealed numerous upregulated and downregulated genes in both male and female model groups. Key genes like KDR, FLT1, PDGFB, and CAV1, and pathways including PI3K-Akt, MAPK, Ras, fluid shear stress and atherosclerosis, calcium signaling, and Rap1 signaling pathways were linked with the disease. Western blot and immunofluorescence analysis confirmed these findings, which were further supported by cell-based experiments. In conclusion, our findings suggest that abnormal expression of specific genes and pathways leading to irregular cell growth, blood vessel formation, and inflammation may be common factors in the pathogenesis of NG in both males and females.

High Population Frequency of GNRHR p.Q106R in Malta: An Evaluation of Fertility and Hormone Profiles in Heterozygotes

Context

The gonadotropin-releasing hormone receptor variant GNRHR p.Q106R (rs104893836) in homozygosity, compound heterozygosity, or single heterozygosity is often reported as the causative variant in idiopathic hypogonadotropic hypogonadism (IHH) patients with GnRH deficiency. Genotyping of a Maltese newborn cord-blood collection yielded a minor allele frequency (MAF) 10 times higher (MAF = 0.029; n = 493) than that of the global population (MAF = 0.003).

Objective

To determine whether GNRHR p.Q106R in heterozygosity influences profiles of endogenous hormones belonging to the hypothalamic-pituitary axis and the onset of puberty and fertility in adult men (n = 739) and women (n = 239).

Design Setting and Participants

Analysis of questionnaire data relating to puberty and fertility, genotyping of the GNRHR p.Q106R variant, and hormone profiling of a highly phenotyped Maltese adult cohort from the Maltese Acute Myocardial Infarction Study.

Main Outcome and Results

Out of 978 adults, 43 GNRHR p.Q106R heterozygotes (26 men and 17 women) were identified. Hormone levels and fertility for all heterozygotes are within normal parameters except for TSH, which was lower in men 50 years or older.

Conclusion

Hormone data and baseline fertility characteristics of GNRHR p.Q106R heterozygotes are comparable to those of homozygous wild-type individuals who have no reproductive problems. The heterozygous genotype alone does not impair the levels of investigated gonadotropins and sex steroid hormones or affect fertility. GNRHR p.Q106R heterozygotes who exhibit IHH characteristics must have at least another variant, probably in a different IHH gene, that drives pathogenicity. We also conclude that GNRHR p.Q106R is likely a founder variant due to its overrepresentation and prevalence in the island population of Malta.

Kisspeptin Treatment Restores Ovarian Function in Rats with Hypothyroidism

Background: Hypothyroidism causes ovarian dysfunction and infertility in women, in addition to being associated with hyperprolactinemia and reduced hypothalamic expression of kisspeptin (Kp). However, it remains unknown whether and how Kp is able to reverse the ovarian dysfunction caused by hypothyroidism. Methods: Hypothyroidism was induced in adult female Wistar rats using 6-propyl-2-thiouracil for 3 months. In the last month, half of the animals received Kp10. Blood samples were collected for dosage of free thyroxine, thyrotropin (TSH), luteinizing hormone (LH), prolactin (PRL), progesterone (P₄), and estradiol (E₂), and uteruses and ovaries were collected for histomorphometry. Body and ovarian weight and the number of corpora lutea were also evaluated. Half of the brains were evaluated by immunohistochemistry to Kp, and the other half had the arcuate nucleus of hypothalamus (ARC) and preoptic area microdissected for gene evaluation of Kiss1, Nkb, Pdyn, and Gnrh1. The pituitary gland and corpora lutea were also dissected for gene evaluation. Results: Hypothyroidism kept the animals predominantly acyclic and promoted a reduction in ovarian weight, number of corpora lutea, endometrial thickness, number of endometrial glands, and plasma LH, in addition to increasing the luteal messenger RNA (mRNA) expression of Star and Cyp11a1 and reducing 20αHsd. An increase in plasma PRL and P₄ levels was also caused by hypothyroidism. Kp immunoreactivity and Kiss1 and Nkb mRNA levels in the ARC and Kiss1 in the anteroventral periventricular nucleus of hypothalamus were reduced in hypothyroid rats. Hypothyroid animals had lower pituitary gene expression of Gnrhr, Lhb, Prl, and Drd2, and an increase in Tshb. The treatment with Kp10 restored estrous cyclicality, plasma LH, ovarian and uterine morphology, and Cyp11a1, 3βHsd, and 20αHsd mRNA levels in the corpora lutea. Kp10 treatment did not alter gene expression for Kiss1 or Nkb in the ARC of hypothyroid rats. Nevertheless, Kp10 increased Lhb mRNA levels and reduced Tshb in the pituitary compared with the hypothyroid group. Conclusions: The present findings characterize the inhibitory effects of hypothyroidism on the hypothalamic-pituitary-gonadal axis in female rats and demonstrate that Kp10 is able to reverse the ovarian dysfunction caused by hypothyroidism, regardless of hyperprolactinemia.

Effect of TSH on oocyte maturation of PCOS patients with normal thyroid function in IVF

BACKGROUND

The serum TSH level of PCOS patients was higher than that of the general female population. For patients with thyroid dysfunction, the abnormal TSH level is negatively related to the outcomes of assisted reproductive technology, but for PCOS patients with normal thyroid function, the effect of TSH level on outcomes of in vitro fertilization has not been reported. In this study, PCOS patients with normal thyroid function were included in this study to evaluate the effect of TSH on the outcomes of IVF-ET.

METHODS

A retrospective cohort study was conducted to analyze the clinical data of 3190 patients who underwent IVF-ET in the Department of Human Reproductive Center of Renmin Hospital Hubei University of Medicine from January 2017 to July 2021, including 594 PCOS patients and 2595 non PCOS patients. The IVF-ET outcomes between the two groups were compared; Multi-factor linear regression analysis was used to analyze the correlation between the related variables and the oocyte maturation of PCOS patients; The ROC curve of the effect of TSH on oocyte maturation in PCOS patients was drawn. The PCOS patients were divided into TSH < 2.98 group (n = 454) and TSH ≥ 2.98 group (n = 141) according to ROC threshold TSH 2.98, and the outcomes were compared.

RESULTS

TSH level in PCOS group was significantly higher than that in non-PCOS group (2.42 ± 0.86 vs 2.00 ± 0.89 UU / ml, P < 0.01), and the oocyte maturation rate and 2PN fertilization rate in PCOS group were lower than those in non-PCOS group (90.9% vs 92.4%, P = 0.02) (84.57% vs 86.77%, P = 0.02). There was no significant difference in cleavage rate and high-quality embryo rate between the two groups (P > 0.05); There was no difference in clinical pregnancy rate, abortion rate, ectopic pregnancy rate and live birth rate between the two groups (P > 0.05). Multi-factor linear regression analysis showed that TSH was negatively correlated with oocyte maturation in PCOS patients [β = -0.124, P = 0.013,95%CI (-0.027 ~ -0.003)]; The oocyte maturation rate in TSH < 2.98 group was significantly higher than that in TSH ≥ 2.98 group (91.7% vs 88.2%, P = 0.001).

CONCLUSION

The TSH level of PCOS patients with normal thyroid function is higher than that of normal people, and it is negatively correlated with the oocyte maturation in in-vitro fertilization. The ROC curve showed that when TSH > 2.98uIU/ml, the possibility of immature oocytes was higher (specificity 28.9%, sensitivity 83.0%).

Dimethyl fumarate improves cognitive impairment by enhancing hippocampal brain-derived neurotrophic factor levels in hypothyroid rats

BACKGROUND

Dimethyl fumarate (DMF) is an effective drug for multiple sclerosis and can improve the cognitive dysfunction caused by streptozotocin, but the effect on cognitive dysfunction caused by hypothyroidism is unclear.

METHODS

After the hypothyroidism rat model induced by propylthiouracil, we gave rats 25 mg/kg DMF by gavage. The body weight during model building and administration was recorded. The levels of T4 and T3 in serum were detected by an automatic biochemical analyzer. Morris water maze test was used to detect the effect of DMF on cognitive learning ability. The effect of DMF on Nissl bodies in the brain tissue was evaluated by Nissl staining. The mRNA and protein levels of BDNF in brain tissue were detected by quantitative reverse transcription-polymerase chain reaction and Western blot. The degrees of p-AKT/AKT and p-CREB/CREB in brain tissue were detected by Western blot.

RESULTS

After DMF treatment, the body weight of hypothyroid rats recovered, and the levels of T3 and T4 in the serum were ameliorated. DMF also reduced the escape latency and distance traveled, and increased the swim speed. The number of Nissl bodies and expression of BDNF, p-AKT/AKT, and p-CREB/CREB in the brain tissue were increased after DMF treatment.

CONCLUSION

DMF improved the cognitive dysfunction of hypothyroid rats by increasing the level of BDNF in the brain tissue of hypothyroid rats.

High normal TSH is associated with lower mannan-binding lectin in women of childbearing age

BACKGROUND

Mannan-binding lectin (MBL) is a main component of the lectin pathway of the complement system. Lower MBL levels are associated with, among other conditions, hypothyroidism and adverse pregnancy outcomes. In turn, adverse pregnancy outcomes and infertility may result from hypothyroidism, even in patients with high normal Thyroid-stimulating hormone (TSH). The aim of this study was to determine if MBL level differs between women of reproductive age with low normal (< 2.5 mIU/l) and high normal (≥2.5 mIU/l) TSH. Associations with other parameters potentially affected by hypothyroidism were also evaluated.

METHODS

Ninety five (95) patients with normal thyroid tests (TSH 0.27-4.2 mIU/l), aged 18-48 years, were prospectively enrolled. Several laboratory parameters were measured, including MBL level, thyroid tests and lipid profile.

RESULTS

Serum MBL level was lower in women with TSH ≥ 2.5 mIU/l than with TSH < 2.5 mIU/l. This association was confirmed by univariate regression analysis. MBL level was significantly lower in patients with abnormally low HDLC/cholesterol ratio and a positive correlation was found between MBL level and HDL/cholesterol ratio.

CONCLUSION

In women of reproductive age with normal thyroid tests, lower MBL is associated with high normal TSH and with less favourable lipid profile. Therefore treatment with L-thyroxine should be considered in women of reproductive age with TSH ≥ 2.5 mIU/l.

Bisphenol A attenuates thyroxine-induced apoptosis in ovarian granulosa cells of pigs

Bisphenol A (BPA) is a chemical of high production volume that is used widely in many industries and is known as a xenooestrogen and anti-thyroid hormone endocrine disrupter. There is little information regarding the effects of BPA in the presence of thyroid hormone on porcine granulosa cell development. Thus, the primary granulosa cells were treated with thyroxine (T4, 10 nM), BPA (10 µM) or T4 plus BPA; we subsequently evaluated the effects of T4 or BPA on 17β-estradiol synthesis, cellular proliferation and apoptosis. Our data showed that BPA significantly increased the accumulation of 17β-estradiol and promoted granulosa cell proliferation, whereas T4 significantly decreased 17β-estradiol and had no effect on cellular proliferation. In addition, it was noteworthy that T4 treatment induced apoptosis in porcine granulosa cells and BPA co-incubation attenuated T4-induced apoptosis as shown from flow cytometric assay analysis. We hypothesized that BPA attenuates T4-induced apoptosis by regulating 17β-estradiol accumulation and oestrogen receptor-mediated signalling pathways. In conclusion, our results demonstrated that T4 affected 17β-estradiol accumulation and induced cellular apoptosis, but did not affect granulosa cell proliferation. Exposure to BPA increased 17β-estradiol accumulation, promoted granulosa cell proliferation and attenuated T4-induced apoptosis in porcine granulosa cells in vitro.

Hyperreactio luteinalis and hypothyroidism: A case report

We report a case of hyperreactio luteinalis (HL) and hypothyroidism diagnosed at 13 weeks of pregnancy. A 29-year-old woman with a spontaneous 13-week singleton pregnancy presented with hirsutism and a pelvic mass. Ultrasound showed a viable pregnancy compatible with the gestational age and multiple cystic lesions on both ovaries. Her TSH levels were markedly elevated and diagnostic of hypothyroidism, for which she was treated. Two days after presentation, she had a spontaneous abortion. The products of conception were histologically normal. Follow-up at 3 months showed resolution of the ovarian cysts, and the previously elevated androgen levels were in the normal range. Hyperreactio luteinalis was diagnosed. Her elevated TSH levels may have contributed to hyperreactio luteinalis through the activation of the hCG receptor.

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Hyperreactio luteinalis is a rare condition, characterized by the enlargement of both ovaries and hyperandrogenism.

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We report a case of hyperreactio luteinalis (HL) and hypothyroidism in a spontaneous 13-week singleton pregnancy.

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Increased levels of thyroid stimulating hormone may have contributed to hyperreactio luteinalis.