IGF-1 Deficiency

This medical condition happens when there is insufficient conversion of GH to IGF-1 by the liver. [24] To determine IGF-1-deficiency, your doctor will order an IGF-1 blood test, or also known as SM-C/IGF-1, Somatomedin-C, and Sulfation factor. IGF-1 blood test is primarily ordered to check for pituitary gland disorders and to assess abnormalities in growth hormone production. [25] An IGF-1 blood test is commonly ordered for patients with symptoms of insufficient or excess production of GH and IGF-1. Unlike GH, the levels of IGF-1 are stable throughout the day, making it a significant indicator of average GH levels. [26]
Causes
Several factors can affect the conversion of GH to IGF-1 by the liver, leading to deficient IGF-1 levels. First and foremost, if there is an existing problem in the principal site of GH to IGF-1 conversion which is the liver, [27] then such conversion may not happen or the liver can only produce little amounts of IGF-1. Also, if there is insufficient amount of GH in the blood, the levels of IGF-1 can fall below the normal. Other factors which can affect IGF-1 levels are pituitary tumors, gene mutations, head injuries or trauma, infections, radiation and surgery. [28] Also, caloric or protein restriction in the diet can decrease the levels of IGF-1 by decreasing the liver cells’ sensitivity to GH stimulation. [29]
Symptoms

In children, the following may indicate IGF-1 deficiency: [30]

• Slowed growth rate in early childhood relative to group norms
• Shorter stature than others of the same chronological age
• Delayed puberty
• X-rays showing delayed bone development

In adults, abnormally low levels of IGF-1 may cause subtle, nonspecific symptoms such as: [31]

• Adverse lipid changes
• Decreased bone density
• Fatigue
• Reduced exercise tolerance