Endocrine Abstracts

Background: Hypopituitary patients with untreated growth hormone deficiency (GHD) have increased fat mass, dyslipidaemia and insulin resistance. Inappropriately low thyroxine doses in patients with central hypothyroidism (CH) may also promote such clinical features.

Objective: To examine metabolic outcome of thyroxine replacement in hypopituitary patients before and after GH replacement.

Method: One thousand and six hundred and two patients with GHD within KIMS (Pfizer International Metabolic Database) were studied before and 2 years after GH treatment. Patients with CH (n=1087) were divided into quartiles (Q1-4) for their L-thyroxine dose per kilogram bodyweight. The CH patients were compared with patients without CH (TSHsuff n=515) and the effect of dose quartiles were evaluated on weight, BMI, waist circumference (WC), waist/hip ratio (W/H), glucose, HbA1c, blood pressure, blood lipids, IGF-I and AGHDA score. Analyses were standardized for gender, age, peak GH level, age of onset and etiology.

Results: Women received higher L-thyroxine dose/kg per day than men, P<0.001. At baseline, weight, BMI, WC, W/H, HDL- and total-cholesterol were higher and glucose, IGF-I and AGHDA score lower in the CH group compared to TSHsuff group. CHQ1 (doses ≤1.08 μg/kg per day) and CHQ2 (doses <1.09–1.36 μg/kg per day) had increased weight, blood pressure and serum IGF-I and decreased AGHDA score compared with CHQ4 (doses ≥1.71 μg/kg per day), P<0.05. In addition, CHQ2 patients had increased WC and W/H compared to CHQ3 and CHQ4. Similarly, W/H was larger in CHQ1 compared to CHQ3. After 2 years of GH treatment CHQ1 lost weight, whereas the other quartiles gained, P<0.05. IGF-I increased more in the CH patients than in TSHsuff group but this was not affected by thyroxine dose/kg.

Conclusion: Subjects with doses of thyroxine ≥1.37 μg/kg per day resembled TSHsuff patients in metabolic endpoints more than CH patients with lower doses. The metabolic profile of CH patients with thyroxine doses ≤1.36 μg/kg per day suggests that they have signs of hypothyroidism and are inadequately treated.