INTRODUCTION

Pulmonary function changes are associated primarily with aging but ovarian hormones also have a certain impact on them. All sex steroid hormone receptors have been shown to be expressed in lung tissue.¹ A new hormonal pattern is established at menopause which is characterized by a rise in the circulating levels of follicle-stimulating hormone and luteinizing hormone and comparatively low levels of estrogen and progesterone.² In postmenopausal women, along with other organ system dysfunctions, lung functions are also adversely affected.³ The respiratory system undergoes various structural, physiological, and immune changes with age. There is an increase in airspace size with aging, resulting from the loss of supporting tissue. Loss of lung function occurs quickly in postmenopausal women, and respiratory muscle strength decreases with age.^4,5 Several studies have reported about hyperventilation and bronchial relaxation being associated with high progesterone levels during luteal phase of menstrual cycle.^6,7 Thus, decreased pulmonary function can be attributed to low levels of sex hormones in postmenopausal women.

Therefore, our study was undertaken with the objective of observing serum levels of sex hormones estrogen and progesterone and to identify its effects on pulmonary function in pre- and postmenopausal women.

MATERIALS AND METHODS

A cross-sectional study was carried out in Department of Obstetrics and Gynecology in Indira Gandhi Government Medical College & Hospital (IGGMC), Nagpur, India, after taking approval from institutional ethical committee. A total of 50 women in premenopause (group I) and 50 women with menopause (group II) were included in our study. Women in group I were staff working in IGGMC Nagpur and were assessed twice once on 10 to 14 days (group I₁) and then on 18 to 22 days (group I₂) of menstrual cycle. Women in group II were selected from patients coming in gynecology outpatient department. After taking past, personal, and family history, complete physical examination was done. After taking written informed consent, pulmonary function of all subjects was measured with digital micro spirometer and data collected. Peak expiratory flow rate (PEFR), forced expiratory flow (FEF)_25-75, forced expiratory volume in 1 second (FEV₁), and forced vital capacity (FVC) were studied and correlated with symptoms. Five milliliters of venous blood was collected under aseptic precaution in both groups and serum estrogen and progesterone levels were estimated using microparticle enzyme immunoassay. Data collected were analyzed using unpaired t-test and Chi-square test.

RESULTS

Mean percentage of predicted values of FEF_25–75 and PEFR was lower in group II as compared with groups I₁ and I₂ (Tables 1 and 2).

The FEV₁ and FVC also were lower in postmenopausal women but there was no significant difference (Tables 1 and 2).

Mean serum estrogen level was significantly lower in group II as compared with groups I₁ and I₂ (Tables 3 and 4).

Mean progesterone level was significantly lower in group II as compared with group I₂ but not with group I₁. Mean progesterone level was significantly lower in group I₁ as compared with group I₂ (Tables 3 and 4).

DISCUSSION

Most of the postmenopausal women in our country fail to avail the existing health care services and thus suffer from complications due to poor lung function. In postmenopausal women, relationship between low level of estrogen and progesterone and the changes in FEF_25–75 and PEFR has been explored by several investigators of different countries.^8-10 In this study, mean percentage of predicted values of FEF_25-75 and PEFR was lower in postmenopausal women.

Various mechanisms have been proposed for these observed changes in lung function in postmenopausal women. After menopause, the ovaries become less functional and there is a reduction in the amounts of estrogen and progesterone produced by the ovary. A few studies have suggested that progesterone induces hyperventilation through both the central medullary and peripheral chemoreceptors.¹¹ Estrogen and progesterone have been associated with relaxation of airway smooth muscles mediated by relaxation of bronchial muscles and widening of bronchi.¹² The bronchial epithelium and smooth muscle contain alpha₂ adrenergic receptors which cause bronchodilation and increase secretion.¹¹

Progesterone has beneficial effects on the upper airway function and breathing is supported by pharyngeal dilator muscle activity.¹³ All these effects are contributed by estrogen and progesterone to increase lung function. Estrogen increases the number of progesterone receptors, therefore, combining effect of estrogen with progesterone increases lung function.¹⁴ After menopause, there is a significant loss of bone mineral density.¹⁵ The cause of the bone loss after menopause is primarily due to estrogen deficiency.¹⁶ As a result, bone mass density in the bones of thoracic cage is also reduced.³ Due to deformities of bones of the thoracic cage, there is decrease in intrathoracic space which is related to decreased lung function.¹⁷ Various investigators suggested that estrogen and progesterone cause increase in muscle strength and induce skeletal myoblast growth.¹⁸ Decreased estrogen and progesterone levels decrease strength of respiratory muscle. However, the exact mechanisms involved in lower lung function in postmenopausal women of the present study cannot be elucidated from this type of study. According to the suggestions made by different investigators,^8,9 lower percentages of predicted values of FVC and FEV₁, PEFR, and FEF_25-75 in postmenopausal women in comparison to premenopausal women during follicular and luteal phase are most likely due to decreased level of progesterone and estrogen as observed in this study. Reduced levels of estrogen and progesterone would cause decreased muscular strength, decreased relaxation of bronchial smooth muscle, and increased compression of thoracic spine and as a result there is reduced total lung capacity.

CONCLUSION

Sex hormones play an important role in women’s lung health. A close relationship between the sex hormones and pulmonary function has been observed in postmenopausal women. It may be concluded that reduced lung function in postmenopausal women may be related to their low estrogen and progesterone level.