title: Acute TSH stimulation in vivo does not alter serum PCSK9 levels.
abstract: BACKGROUND
  It is now recognized that TSH can act on targets other than the thyroid, including the liver. Elevated serum TSH levels in euthyroid subjects were recently reported to correlate with high values of serum proprotein convertase subtilisin/kexin type 9 (PCSK9). This protein, expressed and secreted by hepatocytes, promotes higher LDL-cholesterol levels. We tested whether an acute increase of TSH levels following administration of TSH in vivo would raise PCSK9 levels in patients who had previously undergone total thyroidectomy and radioablation for thyroid cancer.
  
  
  RESULTS
  TSH levels rose from 0.64 ± 1.02 mU/L on day 1 to 98.66 ± 4.83 mU/L on day 3, following injections of recombinant human TSH (on days 1 and 2). PCSK9 levels were 330 ± 99 ng/ml on day 1, and did not change on days 3 or 5 in response to TSH stimulation.
  
  
  CONCLUSIONS
  Although a positive correlation between TSH and PCSK9 in euthyroid subjects has raised the possibility that TSH might act on the liver to raise PCSK9 values, our data show that PCSK9 levels are not affected by acute elevations of TSH levels. Whether chronic elevations of TSH are needed to upregulate PCSK9 remains to be determined.
authors.affiliation: Chronic Disease Program, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada ; Department of Medicine, University of Ottawa, Ottawa, Canada ; Department Biochemistry, Microbiology &Immunology, University of Ottawa, Ottawa, Canada.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Gagnon
authors.affiliation: Chronic Disease Program, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada ; Department of Medicine, University of Ottawa, Ottawa, Canada.
authors.forename: Moeber
authors.initials: M
authors.lastname: Mahzari
authors.affiliation: Chronic Disease Program, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada ; Department of Medicine, University of Ottawa, Ottawa, Canada.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Lochnan
authors.affiliation: Chronic Disease Program, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada ; Department of Medicine, University of Ottawa, Ottawa, Canada ; Department Biochemistry, Microbiology &Immunology, University of Ottawa, Ottawa, Canada ; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Sorisky
keywords: Liver; PCSK9; TSH; Thyroid