Central Hypothyroidism and Its Replacement Have a Significant Influence on Cardiovascular Risk Factors in Adult Hypopituitary Patients

Abstract

Thyroid dysfunction may have detrimental effects on patient outcomes. Few studies have assessed this issue in patients with secondary hypothyroidism. Our objective was to test the hypothesis that thyroid hormone status has an impact on cardiovascular risk factors in adult patients with hypopituitarism. This was a retrospective observational study (1993-2012) at a tertiary referral university hospital. All GH-deficient patients starting GH replacement (1993-2009) with measured free T4 (fT4) (n = 208). Baseline fT4 defined patients as TSH-sufficient and TSH-deficient (further divided into tertiles according to baseline fT4; first tertile had lowest fT4). Anthropometric (body mass index [BMI], waist circumference, total fat (fat mass) and lean body mass [LBM]) and biochemical (lipids and fasting plasma glucose) data were collected at baseline and a median 4.1 years after commencement of GH. At baseline, fT4 was negatively associated with BMI and waist circumference, but positively with high-density lipoprotein, independent of age, gender, and IGF-I (SD score). Only first-tertile TSH-deficient patients had higher BMI (P = .02), fat mass (P = .03), total cholesterol (P = .05), triglycerides (P < .01), and waist circumference (P = .01), and lower high-density lipoprotein cholesterol (P = .03) as compared with TSH-sufficient patients. At follow-up, IGF-I, LBM, and plasma glucose had increased in all subgroups (P < .01). The change in fT4 (ΔfT4) (follow-up - baseline) was negatively correlated to ΔBMI, ΔLBM, Δtotal cholesterol, and Δlow-density lipoprotein cholesterol (all P < .05, adjusted for ΔIGF-I and ΔGH and hydrocortisone dose). The negative correlation to Δtotal cholesterol and Δlow-density lipoprotein cholesterol persisted only in first-tertile TSH-deficient patients. This single-center study over a 20-year period has strengthened the importance of improved awareness of thyroid status and optimal thyroid replacement of hypopituitary patients to reduce cardiovascular risks in hypopituitary patients.