Low-density lipoprotein apolipoprotein B100 turnover in hypopituitary patients with GH deficiency: a stable isotope study.
BACKGROUND
Epidemiological studies suggest that hypopituitary patients have an increased risk for cardiovascular mortality. The dyslipidaemia associated with this condition is often characterised by an increase in total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol (LDL-C) and may contribute to these findings. The underlying mechanisms are not fully elucidated.


METHODS
LDL apolipoprotein B (apoB) production rate and metabolic clearance rate were measured in seven patients with hypopituitarism (including GH deficiency) under stable conventional replacement therapy (three males and four females; age 40-16.1 years; body mass index 29.0-6.1 kg/m(2) (means +/- s.d.)) and seven age-, gender- and body mass index-matched control subjects with an infusion of 1-(13)C-leucine. Fasting lipid profile and lipid composition of LDL were also measured.


RESULTS
Fasting TC, triglycerides (TG), high-density lipoprotein-C, LDL-C and free fatty acid concentrations were not different between hypopituitary patients and control subjects. LDL-TG (P < 0.006) and LDL-TG/LDL apoB ratio (P < 0.02) were significantly increased in hypopituitary patients. LDL apoB pool size was not statistically different between patients and control subjects. In the hypopituitary patients, LDL apoB metabolic clearance rate (P < 0.05) and LDL apoB production rate (P < 0.02) were lower than in the control subjects.


CONCLUSIONS
The present results suggest that LDL apoB turnover and LDL composition is altered in hypopituitary patients. Whether these findings explain the increased risk for cardiovascular disease in hypopituitary patients remains to be established.
Department of Endocrinology and Diabetology, University Hospital of Bern, Switzerland.
Emanuel R
ER
Christ
Michael H
MH
Cummings
Michael
M
Stolinski
Nicola
N
Jackson
Peter J
PJ
Lumb
Anthony S
AS
Wierzbicki
Peter H
PH
Sönksen
David L
DL
Russell-Jones
A Margot
AM
Umpleby
D000328:Adult; D000367:Age Factors; D001055:Apolipoproteins B / Q000378:metabolism*; D001057:Apolipoproteins E / Q000097:blood; D015992:Body Mass Index; D002247:Carbon Isotopes; D050171:Dyslipidemias / Q000150:complications; D005260:Female; D013006:Growth Hormone / Q000627:therapeutic use; D020249:Hormone Replacement Therapy; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007018:Hypopituitarism / Q000188:drug therapy / Q000378:metabolism*; D008055:Lipids / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics
D001055:Apolipoproteins B; D001057:Apolipoproteins E; D002247:Carbon Isotopes; D008055:Lipids; D008077:Lipoproteins, LDL; D019382:Human Growth Hormone; D013006:Growth Hormone