Hypothalamic–pituitary-end organ function in women with bipolar depression

Abstract

Disturbance of each of the three hypothalamic-pituitary-end organ systems [hypothalamic-pituitary-thyroid (HPT), -adrenal (HPA), and -gonadal (HPG)] has been reported in depressive disorders. Little is known about potential reciprocal interaction among the three HP-end organ systems in patients with depressive disorders. The present pilot study examined selective HPA and HPG hormones in a detailed time series in women with bipolar disorder (depressed type) before and after treatment with levothyroxine (L-T4), and in matched control subjects. Six medically stable, euthyroid, premenopausal women with bipolar depression, and 5 age-matched controls underwent overnight blood sampling from 2100 to 0900 h for measurement of adrenocorticotropic hormone (ACTH), cortisol, luteinizing hormone (LH), and estradiol every 15 min. Bipolar patients underwent a second overnight blood sampling procedure following 7-weeks of open-label add-on treatment with L-T4. Results revealed lower baseline cortisol parameters in bipolar patients in comparison to control subjects, while ACTH, LH, and estradiol parameters were similar. Thyroid hormones (TSH, free and total T4) were not correlated with any of the HPA or HPG hormones. ACTH and cortisol levels were correlated in control subjects, but not in bipolar patients. After L-T4 treatment, thyroid hormones increased significantly and depression scores significantly declined. No significant changes in HPA or HPG hormones parameters were observed, although the small sample size may have limited results. Upon visual inspection, ACTH and cortisol appeared to decrease after L-T4 treatment, while estradiol appeared to increase. These pilot data suggest lower levels of cortisol in women with bipolar depression, unlike previously published studies that reported higher cortisol in patients with depression. The data also suggest reciprocal changes in the HPA and HPG axes upon pharmacological modulation of the HPT system, although whether this change was due to the L-T4 treatment or the improvement of depression is unknown. The results are preliminary, and require replication in larger samples.