Thyroid hormonal changes among women with polycystic ovarian syndrome in Baghdad – a case-control study

Introduction

Polycystic ovarian syndrome (PCOS) is a condition of ovarian dysfunction characterized by hyperandrogenism and polycystic ovaries. The global prevalence of polycystic ovaries among women is 25%¹. PCOS is a state of insulin resistance, which is considered to be the main factor contributing to development of the syndrome; diagnosis is based on the presence of two out of three of the following: clinical and/or biochemical androgen excess, anovulation and polycystic ovaries on pelvic ultrasound². The mechanisms behind these include hyperinsulinemia, disruption of the hypothalamic–pituitary–gonadal axis, dysregulation of ovarian steroidogenesis, as well as genetic and environmental factors^2,3. PCOS mainly affects women in aged 18–35^3,4. Previous studies have documented ovarian enlargement and cystic transformation in thyroid disorders^5–8. Thyroid disorders and PCOS are of widespread in the general population, however, the precise nature of the relationship between the two disorders is not currently know. Although the pathophysiology of thyroid disorder and PCOS are totally different⁶. Whether this is due to some common factors predisposing an individual to both disorders, or due to a pathophysiological connection between the two disorders has yet to be established⁵. Two factors making the picture more interesting, are that both have different etiopathology, and that reportedly thyroid disorders are more common in PCOS subjects^7–9. PCOS begins soon after menarche age as a endocrinologic abnormality, two most common endocrine symptoms are chronic elevation of luteinizing hormone (LH) and insulin resistance^4,7,9. The genetic cause of high LH is unknown. Interestingly, neither an elevation in LH nor insulin resistance alone is enough to initiate the PCOS^7,9. High LH and hyperinsulinemia work synergistically, causing ovarian growth, androgen production, and ovarian cyst formation^4,5,9. The thyroid gland regulates the rate at which the body converts food for energy, functioning as a thermostat to control the body’s metabolism and other systems. If it secretes hormones too fast will increase metabolism and lead to hyperthyroidism, the inverse leads to slow metabolism, resulting in weight gain and hypothyroidism^4,5. However, it is not yet known whether this is because of factors predisposing an individual to both disorders or a pathophysiological connection between the two disorders.

Methods

Results

The average age of participants was 27.7±4.7 years for the PCOS group and for the control group 26.8±4.7 years. All patients lived in urban cities in Baghdad province. The PCOS group exhibited significantly higher mean body mass index (BMI; 28.6 vs. 24.9 kg/m²) and LH level (15.2 vs. 4.7 mIU/mL) and a non-significantly higher FSH level (9.2 vs. 5.2 mIU/L) than the control group, (P-values <0.001, <0.001, <0.007, <0.001, respectively) (Table 1 and Underlying data¹³). There was a significant association between (P-value <0.003) increased body weight and PCOS; while 86% of patients in the PCOS group were overweight or obese, the proportion of overweight/obese patients in the control group did not exceed 50% (Table 2, Table 3). The proportion of patients with elevated TSH levels was significantly greater in the PCOS group than in the control group (52% vs. 10%). At the same time, it is was significant to find that one-fourth of patients in the PCOS group (24%) showed decreased T3 levels (compared to 0% in the control group). There was a significant and direct correlation between age and T4 level, with increase in age being associated with a coefficient of increase of 0.238 in T4 level. This association was significant only in the PCOS group, in which increase in age was associated with a coefficient of increase of 0.294 per year in T4 level (P-value <0.001), (Table 3). Thyroid function parameters (TSH, T3, and T4 levels) were not correlated with BMI or LH or FSH level. Among the 50 patients with PCOS, 20 (40.4%) had subclinical hypothyroidism (SCH) and 30 (59.6%) were euthyroid (P-values <0.003, <0.001), (Table 4).

Discussion

PCOS is the most common disorder among young women and an important cause of infertility in this age group. PCOS and thyroid disorder are two of the most common endocrine disorders in women, and while these conditions are very different. Hypothyroidism, is more common in women with PCOS than in the general population. Thyroid and PCOS are interconnected by both genetic and environmental factors which are believed to be contributing to thyroid disorders in PCOS, and is known to cause PCOS-like ovaries and overall worsening of PCOS and insulin resistance.

The most obvious connection between thyroid diseases and PCOS seem to be an increase in BMI, which is very prevalent in women with PCOS, observed than control group, (BMI for PCOS =28.6±4.0; BMI for control= 24.9±3.0 with P-value=<0.001).

In the present study, 20 (40%) of 50 patients with PCOS showed SCH. In a previous study, Michalakis et al. reported an SCH prevalence of 23% among patients seeking treatment for infertility, while another study reported a prevalence of 17.5% among patients with PCOS¹⁴.

A few studies have previously analyzed the prevalence of SCH in subjects with PCOS. Subclinical hypothyroidism is observed among women with PCOS, with an estimated prevalence range of 10–25%⁹. Regarding the impact of subclinical hypothyroidism on the clinical, hormonal or metabolism of women with PCOS, a recent meta-analysis has shown that the coexistence of SCH and PCOS leads to mild alterations in serum lipids, but not in hormone levels (TSH, FSH, LH and their ratio)⁹.

The findings of the present study are similar to those of a study by Enzevaei et al. in Iran, where 25.5% of subjects with PCOS were found to have SCH¹⁵. Similarly, in a study by Sinha et al. in India, 22.5% subjects with PCOS were reported to have SCH compared to 8.75% in controls and thyroid antibodies have been shown to be present in 27% of patients with PCOS versus 8% in controls¹⁶, also indicated the presence of elevated—T3, T4, TSH in patients with PCOS¹⁷. Kachuei et al. have also reported a significantly higher prevalence of anti-thyroglobulin antibodies in subjects with PCOS than in control subjects in an Iranian population¹⁸.

Examination and radiology investigations alone is not a reliable test to determine PCOS. TSH measures, T4, and T3 may be more applicable in the diagnosis of PCOS. Relying the combinations of all these is sufficient to make an accurate diagnosis and reason why so many people with PCOS and hypothyroid are not misdiagnosed.

Conclusion

We conclude that most patient with PCOS will have some degree of thyroid dysfunction, especially SCH. PCOS is much more than just oligomenorrhea, amenorrhea, or infertility. Doctors must be aware of the risk factors for PCOS and intervene with a preventive approach, which may restore normal menstrual function, ovulation, and fertility. Therefore, physicians should consider screening for thyroid function tests at PCOS diagnosis, even in the absence of symptoms related with thyroid dysfunction.

Data availability