Unmasking of type III hyperlipoproteinemia by hypothyroidism: a dramatic illustration of altered lipoprotein metabolism in a postpartum woman.
OBJECTIVE
To illustrate the potential abnormalities in lipoprotein metabolism associated with type III hyper-lipoproteinemia and the modulation of their clinical expression by thyroid hormone and estrogenic status.


METHODS
An illustrative case, with associated clinical and laboratory data, is presented, and relevant clinical and pathophysiologic studies from the literature are reviewed.


RESULTS
A 35-year-old woman, at 7 months after delivery of her first child, presented to her family physician with a complaint of painful eruptions on the palms of her hands. On evaluation, she was found to have new hypothyroidism and severe hypertriglyceridemia (>1,569 mg/dL). Thyroxine replacement was initiated, and she was referred to the lipid clinic. When seen in the lipid clinic shortly thereafter, her triglyceride level had normalized, but her low-density lipoprotein (LDL) fraction was strikingly elevated (representing a combination of elevated intermediate-density lipoprotein and LDL cholesterol). On physical examination, palmar xanthomas were noted, suggestive of type III hyperlipoproteinemia. This diagnosis was further supported by homozygosity at the apolipoprotein E (apo E) gene locus for the apo E2 allele implicated in this condition. Ultimately, with attainment of euthyroidism in the subsequent weeks, the lipid profile normalized, with the LDL cholesterol concentration particularly reduced at 55 mg/dL.


CONCLUSIONS
Clinical expression of type III hyperlipoproteinemia necessitates interaction between an underlying genetic defect of lipoprotein metabolism (apo E2 homozygosity) and a secondary metabolic insult such as, in the current case, hypothyroidism and possibly breast-feeding-mediated hypoestrogenemia. As such, in patients with type III hyperlipoproteinemia, it is essential to search for exacerbating factors, particularly because the amelioration of such factors may rectify the effects of the underlying dyslipidemia.
Retnakaran
Ravi
R
Department of Medicine, Division of Endocrinology, St. Michael's Hospital and Health Centre, 61 Queen Street East, Toronto, Ontario, Canada.
Connelly
Philip W
PW
Goguen
Jeannette
J
D000328:Adult; D002784:Cholesterol / Q000097:blood; D015897:Comorbidity; D005260:Female; D006801:Humans; D006952:Hyperlipoproteinemia Type III / Q000150:complications* / Q000175:diagnosis*; D007037:Hypothyroidism / Q000150:complications*; D008074:Lipoproteins / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D049590:Postpartum Period; D013972:Thyrotropin / Q000097:blood; D014280:Triglycerides / Q000097:blood; D014973:Xanthomatosis / Q000175:diagnosis
D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D014280:Triglycerides; D013972:Thyrotropin; D002784:Cholesterol