Zomacton Mechanism of Action

Pharmacotherapeutic group: Somatropin and somatropin agonists. ATC code: H01AC01.
Pharmacology: Pharmacodynamics: ZOMACTON contains somatropin, which is human growth hormone produced by recombinant DNA-technology. Somatropin is a potent metabolic hormone of importance for the metabolism of lipids, carbohydrates and proteins.
Pharmacodynamic properties: Identical to pituitary derived human growth hormone (pit‑hGH) in amino acid sequence, chain length (191 amino acids) and pharmacokinetic profile. ZOMACTON can be expected to produce the same pharmacological effects as the endogenous hormone.
Skeletal system: ZOMACTON treatment stimulates growth of the skeletal bone in paediatric patients with confirmed deficiency of endogenous hGH.
The measurable increase in height after administration of ZOMACTON results from an effect on the epiphyseal plates of long bones. In children who lack adequate amounts of endogenous hGH, ZOMACTON produces increased growth rates and increased IGF 1 (Insulin like Growth Factor/Somatomedin-C) concentrations that are similar to those seen after therapy with endogenous hGH. Elevations in mean serum alkaline phosphatase concentrations are also involved.
Other organs and tissues: An increase in size, proportional to total increase in body weight, occurs in other tissues in response to growth hormone, as well. Changes include: increased growth of connective tissues, skin and appendages; enlargement of skeletal muscle with increase in number and size of cells; growth of the thymus; liver enlargement with increased cellular proliferation; and a slight enlargement of the gonads, adrenals, and thyroid.
Disproportionate growth of the skin and flat bones, and accelerated sexual maturation have not been reported in association with the growth hormone replacement therapy.
Protein, carbohydrate and lipid metabolism: Growth hormone exerts a nitrogen retaining effect and increases the transport of amino acids into tissue. Both processes augment the synthesis of protein. Carbohydrate use and lipogenesis are depressed by growth hormone. With large doses or in the absence of insulin, growth hormone acts as a diabetogenic agent, producing effects seen typically during fasting (i.e. intolerance to carbohydrate, inhibition of lipogenesis, mobilisation of fat and ketosis).
Mineral metabolism: Conservation of sodium, potassium, and phosphorous occurs after treatment with growth hormone. Increased calcium loss by the kidney is offset by increased absorption in the gut. Serum calcium concentrations are not significantly altered in patients treated with ZOMACTON or with pit‑hGH. Increased serum concentrations of inorganic phosphates have been shown to occur both after ZOMACTON and pit‑hGH. Accumulation of these minerals signals an increased demand during tissue synthesis.
Pharmacokinetics: Eight healthy subjects received 0.1 mg somatropin/kg body weight. Peak plasma levels of about 64 ng/ml were found 6 hours after administration.