Regarding albumin

Regarding albumin, the following statements are true EXCEPT which one?

a) Albumin is a negative acute phase protein
b) A common cause of hypoalbuminaemia is starvation or malnutrition
c) In health the liver produces approximately 10 g per day of albumin
d) The circulation half-life of albumin is approximately 18 days
e) The majority of total body albumin is found in the extravascular compartment

Answer: b

Explanation
Albumin is a single polypeptide of 585 amino acids and molecular weight 66kDa
produced by the liver. Its molecular weight is variably quoted between 66 and
69kDa, which seems to be related to the degree of glycosylation. It is negatively
charged and very soluble, and performs a number of crucial physiological roles. It is
the most abundant plasma protein, responsible for maintenance of colloid oncotic
pressure and transport, via protein-binding, of drugs, bilirubin, thyroid hormones,
calcium ions and more. Despite its domination of plasma proteins, only 40% of total
body albumin is intravascular. The rest is in the interstitial compartment having been
filtered from the intravascular compartment (the transcapillary escape rate is 5% per
hour) and slowly returned to the circulation via the thoracic duct. It performs similar
roles in the interstitium, including exerting an oncotic pressure (consider Starling
forces). However, although the interstitial albumin content is greater, the volume in
which it resides is significantly greater such that resultant oncotic pressure is low and
the gradient is maintained. It is a common misconception that serum albumin concentration
is a marker of nutritional status and that it falls in starvation. It is correct that
albumin is not stored in the liver so levels do reflect synthetic activity but during
starvation with normal liver function, albumin will be maintained at the expense of
proteolysis elsewhere. Albumin is not catabolised during starvation. It is common,
however, that malnutrition accompanies disease states that are associated with hypoalbuminaemia.
The causes of low albumin states are categorised into decreased synthesis
(liver dysfunction), increased loss (e.g. renal dysfunction), redistribution
(i.e. capillary leak) and very rarely increased catabolism. Acute and chronic inflammatory
states provoke elements of each of these. Also albumin is referred to as a negative
acute phase reactant as its manufacture is diminished as part of the inflammatory
process.