50. Hypo-, hyper- and dys-proteinemia
Hyperproteinaemia
Hyperproteinaemia occurs most commonly due to excessive protein intake. It can also occur due to dysproteinaemia or paraproteinaemia, discussed later.
The RDA for adult males is 56 g protein every day. The requirement is 46 g in females and 71 g in pregnant or breastfeeding women. The requirement is higher in people who are physically active. Around 1 – 1.6 g of protein per kg of body weight is recommended for people who exercise depending on the intensity level of the exercise.
Normal people can typically consume up to 2 g of protein per kg body weight long-term without any significant side effects. Elite athletes may consume up to 3.5.
The actual level of proteins in the blood depends on the intake and on the consumption. If the intake of proteins is very high but the consumption is too (due to bodybuilding or something), the protein level in the blood won’t rise to dangerous levels. Protein is also an energy source, so much of the excess protein is burnt for energy as well.
Potential adverse effects of hyperproteinaemia include disorders of bone and calcium homeostasis, disorders of renal function and gout.
Adverse effects of hyperproteinaemia
Bone homeostasis
Excessive protein consumption increases urinary calcium excretion and bone resorption. This may predispose to bone fractures and osteoporosis.
Renal function
High protein consumption may increase the incidence of kidney stones. It also increases the GFR by tubuloglomerular feedback. The transport capacity of the tubules is overloaded, which causes proteinuria. This contributes to renal disease by the mechanisms described in topic 69 in pathophys 1.
Gout
Foods that are high in proteins are often also high in purines, which may increase the risk for gout.
The book claims that excessive protein intake increases the risk for polyglobulia and allergy, but I couldn’t find any literature that supports those claims.
Dysproteinaemia
Dysproteinaemia refers to an altered composition of the plasma proteins. It’s usually due to decreases in albumin level or increases in the level of acute phase proteins due to inflammation. It may also occur in cancer, nephrotic syndrome, cirrhosis or autoimmune diseases.
Paraproteinaemia is a special form of dysproteinaemia where a protein that is normally absent from the plasma begins to appear in high numbers. It’s usually associated with plasma cell dyscrasias, which produce abnormal immunoglobulins like M proteins and Bence-Jones proteins.
Hypoproteinaemia
The decreased amount of protein in the blood is usually seen in:
- Insufficient protein intake or absorption
- Liver failure
- Burns
- Nephrotic syndrome
The consequence depends on which protein(s) is deficient. Hypoproteinaemia increases the activity of the liver, causing it to produce more lipoproteins and coagulation factors. Oedema may develop due to reduced oncotic pressure.