Gigantism in cats, or feline acromegaly, is a rare endocrine disorder caused by a growth hormone-secreting pituitary tumor. It causes excessive growth, insulin-resistant diabetes, and abnormal enlargement of organs, primarily affecting older male cats. Map & Directions Clinical Pathology Laboratory Monday-Friday: 7:00 a.m. – 10:00 p.m. ET Saturday-Sunday: 9:00 a.m. – 10:00 p.m. ET The Clinical Pathology section is located in the Veterinary Medical Center on the main MSU campus. All other laboratory sections are in the MSU VDL facility located south of the main campus. Laboratory Assessment for Growth Hormone Abnormalities in Cats Growth hormone (GH) is produced in the anterior pituitary gland and is normally under the control of the hypothalamus via growth hormone-releasing hormone (GHRH). Growth hormone is challenging to measure directly for several reasons, both physiologically and from a laboratory perspective. Growth hormone is produced in a pulsatile fashion, is highly influenced by various physiological states, and has a short half-life in the blood stream. In addition, growth hormone is not well conserved among species making assay availability problematic. Insulin-like growth factor 1 (IGF-1) is produced primarily in the liver in response to growth hormone stimulation. IGF-1 has a much longer half-life compared to growth hormone, is produced in a non-pulsatile manner, is stable in serum, and is well-conserved between species. These features make IGF-1 a suitable substitute for direct measurement of growth hormone, and IGF-1 results can be expected to reflect growth hormone production in dogs and cats. Serum or plasma may be submitted for IGF-1 testing (20005). Effects of excess growth hormone include peripheral and hepatic insulin resistance, resulting in both reduced cellular uptake of glucose and decreased ability to suppress glucose production in the liver. These actions culminate in insulin resistance, marked hyperglycemia, and very often diabetes, which can be difficult to control even with high doses of insulin. Anabolic effects of growth hormone include bone, cartilage and muscle growth, which account for the syndrome of physical changes. Cats with acromegaly may present with polyphagia, prognathia inferior, “clubbed” paws, heart murmur, respiratory stridor from growth of oropharyngeal/lingual tissue, unexpected weight gain, and generalized organomegaly (kidneys and liver). This will affect Moose drastically. As a child, she'll be taller than most of her age group, and slowly grow taller and taller. As she gets older, signs of respiratory stridor will appear, and around 45 moons, one of her vocal chords will become paralyzed, leading to a raspy, breathy voice. Once she's an elder, she will spend most of her time in the medic den, soothing the pain.
