Epidemiology of reproductive and hormonal factors in thyroid cancer: Evidence from a case‐control study in the Middle East

Abstract

Thyroid cancer is the second most common neoplasm among women in Kuwait and several other countries in the Middle East. Most of these countries also have relatively high birth and total fertility rates. To examine potential relationships between reproductive and hormonal factors and thyroid cancer, we conducted a population-based case-control interview study among 238 women diagnosed with thyroid cancer and a similar number of individually matched controls in Kuwait. Among the demographic variables, women with 12؉ years of education had a significantly reduced risk of thyroid cancer (OR ‫؍‬ 0.4; 95% CI: 0.2-0.8; p-trend <0.05). The average age at diagnosis (؎SD) of thyroid cancer was 34.7 ؎ 11 years. Events such as age at menarche, pregnancy, menopausal status and age at menopause were not associated with thyroid cancer. There was an association with age at last pregnancy and parity. Women who had their last pregnancy at ages >30 years were at a significantly increased risk (OR ‫؍‬ 2.1; 95% CI: 1.2-3.8); there was also a significant trend in risk with increasing age at last pregnancy. There was a modest increase in risk among women who had borne >5 children (OR ‫؍‬ 1.5; 95% CI: 0.9 -2.5). A joint analysis of these factors showed that childbearing during the latter half of reproductive life had a substantial effect on the incidence of thyroid cancer; for any given level of parity, there was about a 2-fold increased risk if the age at last pregnancy was >30 years. A substantial recent-birth effect, in relation to subsequent diagnosis of thyroid cancer, was observed during the second and third year after a birth (OR ‫؍‬ 2.0; 95% CI: 1.0 -4.1). In contrast, spontaneous abortion seemed to have a protective effect. There was a significant decrease in risk among women who had a miscarriage as outcome of first pregnancy (OR ‫؍‬ 0.1; 95% CI: 0.03-0.4) and those who had experienced >3 miscarriages (OR ‫؍‬ 0.3; 95% CI: 0. Thyroid cancer is a relatively rare form of cancer that occurs 2-3 times more frequently among females. In most countries, it accounts for approximately 1-5% of all cancers in females and Ͻ2% in males. 1 This female predominance, which is greatest during reproductive ages, is observed in all geographical areas and ethnic groups. The age-standardized incidence rates (per 100,000) of thyroid cancer, across most populations, vary from approximately 2-10 in females and 1-3 in males. 1 As thyroid cancer and the majority of benign thyroid disorders (e.g., Graves disease, non-endemic goitre, Hashimoto thyroiditis) are significantly more common in women, a major effort has focused on examining the influence of reproductive and hormonal factors in the etiology of diseases of the thyroid gland. An international collaborative group has recently published a series of overviews by pooling data from all the case-control studies of thyroid cancer published during the period 1980 -97 (n ϭ 12) and 2 unpublished studies. [2][3][4] The epidemiology of thyroid cancer has been comprehensively reviewed by Franceschi et al., 5 ...

Benign thyroid disease and dietary factors in thyroid cancer: a case–control study in Kuwait

“…This is perhaps the first indication in the literature of a possible link between history of post-partum thyroiditis and thyroid cancer. The finding has been discussed in a separate paper (Memon et al, 2002). Overall, individuals with a history of any benign thyroid disease were at a considerably high risk of developing thyroid cancer (OR=6.4; 95% CI: 3.4 -12.0).…”

“…The study population and methods are described in detail elsewhere (Memon et al, 2002). Briefly, our study was conducted at the Kuwait Cancer Control Centre (KCCC) which is the only specialised cancer treatment and follow-up hospital in the country.…”

The epidemiology of thyroid diseases in the Arab world: A systematic review

“…The sample size found varied from 99 to 749 subjects except for one study conducted in Oman in which 36000 babies were diagnosed. The study population of these studies comprised of children of school age and adults: five studies were case control with sample size varying from 100 to 313 subjects (Akbar et al, 2006;Memon et al, 2002aMemon et al, , b, 2004Memon et al, , 2010; four of the studies were from Kuwait (Memon et al, 2002a(Memon et al, , b, 2004Memon et al, 2010); and one from Saudi Arab (Akbar et al, 2006) and the study population was recruited from hospitals in Kuwait and Saudi Arab, retrospectively, and eight studies were retrospective; three were from Yemenone from Iraq (Nasheiti, 2005), three from Saudi Arab and one from United Arab Emirate. The sample size was found to vary from 45 to 810 subjects and comprised of children and adults, and all data collected were hospital based.…”

A Clinical Study About Incidence of Occult Malignancy in Longstanding Multinodular Goitre

“…(14) but recent studies reported that the use of hormonal therapy of fertility drugs are not associated with thyroid malignancy. (18,19) The availability of more sensitive and better diagnostic tools may be responsible for the increasing incidence of thyroid cancer.…”