Endocrine Case Study (ANSWERED)

Answer the questions concerning this case study:

A child from Nassau, Bahamas, is examined by endocrinologists at a pediatric hospital in Jacksonville, Florida. The child is not exhibiting normal growth. However, the level of circulating GH is relatively high. Additionally, the level of circulating IGF-1 is low. A biopsy of the child’s liver tissue is examined at the hospital’s laboratory. The tissue is observed using a fluorescent microscope. Special fluorescent-labeled antibodies to the GH-binding region of the GH receptor are prepared as diagnostic probes. (Remember that antibodies exhibit specificity to a particular antigen.) It is found that the antibody probe does not bind to the liver tissue of the patient; however, the antibody probe does bind to normal liver tissue. A physician diagnoses the condition as Loran’s syndrome, a very rare genetic disease. This disease has a higher incidence in the Bahamas than other places of the world. Answer these questions:

Why is the child not growing?

The child has a relatively low IGF-1 which helps in bone and overall growth. When deficient, IGF-1 can inhibit the growth of bones and general growth. At the same time, the child is not able to use the growth hormone, which is now in high circulation, thus the Loran’s syndrome.

What accounts for the high GH concentration?

The child’s body is unable to use the Growth hormone, thus, when it is not utilized, its concentration is likely to rise. This is evidenced by the failure of the antibody probe to bind to the liver tissue of the patient.

What accounts for the low IGF-1 concentration?

The growth hormone receptor seems to contribute to the low IGF-1, i.e., GHR makes the child’s resistant to the effects of the GH (growth hormone) and the result are low levels of IGF-1.

Would the patient respond to GH therapy?

No. GH therapy is recommended in patients with GH deficiencies. However, in this case, the patient has high GH circulating the body. Even if the patient were exposed to this therapy, binding the antibody probe would not be possible.

What is the relationship between the liver and epiphyseal plate elongation?

The liver signals the growth hormone by binding to the GH receptor. GH, on the other hand, promotes the growth of long bones. Since the epiphyseal plate/ growth plate provides the site for the growth of long bone, the liver facilitates the action of GH by signalling its binding. Hence, the relationship between the liver and the epiphyseal plate elongation is the facilitation function enabled by the liver to the latter.

What gene is mutated in this condition—receptor gene or hormone gene?

The hormone gene (GHR gene) is mutated in Loran Syndrome

Reference

Racine, H. L., & Serrat, M. A. (2020). The Actions of IGF-1 in the Growth Plate and Its Role in Postnatal Bone Elongation. Current osteoporosis reports, 18(3), 210–227. https://doi.org/10.1007/s11914-020-00570-x