Central hypothyroidism and its replacement have a significant influence on cardiovascular risk factors in adult hypopituitary patients.

CONTEXT: Thyroid dysfunction may have detrimental effects on patient outcomes. Few studies have assessed this issue in patients with secondary hypothyroidism.

OBJECTIVE: Our objective was to test the hypothesis that thyroid hormone status has an impact on cardiovascular risk factors in adult patients with hypopituitarism.

DESIGN AND SETTING: This was a retrospective observational study (1993-2012) at a tertiary referral university hospital.

PATIENTS: 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).

MAIN OUTCOME MEASURES: 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.

RESULTS: 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.

CONCLUSION: 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.