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Understanding the Role of Sexual Hormones in Labrador Development

Sexual hormones play a pivotal role in the overall development and health of Labradors. These hormones are not just a biological aspect; they are essential for the proper maturation of various physical structures. By removing these hormones, you significantly increase the risk of your dog developing serious health problems later in life, which can adversely affect their overall wellness. This hormonal influence is also believed to contribute to what many refer to as the “American Labrador” look, a distinct physical variation that has emerged over time.

The Importance of Hormones in Growth

Labradors require these hormones to facilitate the development of critical physical attributes, including their jaw structure, hips, elbows, and overall bone density, encompassing the head, legs, and ribs. Additionally, these hormones are crucial for the gradual dropping of their chest, an important characteristic of the breed. It is essential to note that Labradors do not reach their full physical maturity until they are between 18 to 24 months old. This developmental phase encompasses various aspects, including height, weight, bone growth, and the maturity of hormones, which collectively contribute to their health and wellness.

Hormones are the drivers of natural growth in the body. When it comes to responsible breeding practices, breeders typically certify the hips and elbows of Labradors at the age of two years. The rationale behind the Orthopedic Foundation for Animals (OFA) checks occurring at 24 months is that this is the age when the growth plates in the joints have closed completely, indicating that the dog has reached its full growth potential. If hormones are removed prematurely, it can lead to improper growth patterns, which may manifest as skeletal issues or other health complications.

A Broader Perspective on Health and Wellness

From a broader perspective, understanding the role of hormones in canine development is paramount for anyone considering breeding or adopting a Labrador. Ensuring that these animals grow up with their natural hormones intact is not only beneficial for their physical appearance but also vital for their long-term health and wellness. The choices made during the early stages of a Labrador's life can have lasting implications, influencing not just their physical attributes but also their quality of life.
In conclusion, the significance of sexual hormones in the development of Labradors cannot be overstated. By allowing these hormones to play their natural role, we support the overall health and wellness of these beloved pets, ensuring they grow into their best selves both physically and emotionally.

STUDY 1
http://www.ncbi.nlm.nih.gov/pubmed/12433723
Cancer Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40.
Endogenous gonadal hormone exposure and bone sarcoma risk.
Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters DJ.

Source:
Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, Indiana 47907, USA.

Abstract
Although, experimental and clinical evidence suggest that endogenous sex hormones influence bone sarcoma genesis, the hypothesis has not adequately tested in an appropriate animal model. We conducted a historical cohort study of Rottweiler dogs because they frequently undergo elective gonadectomy and spontaneously develop appendicular bone sarcomas, which mimic the biological behavior of the osteosarcomas that affect children and adolescents. Data were collected by questionnaire from owners of 683 Rottweiler dogs living in North America.

To determine whether there was an association between endogenous sex hormones and risk of bone sarcoma, relative risk (RR) of incidence rates and hazard ratios for bone sarcoma were calculated for dogs subdivided on the basis of lifetime gonadal hormone exposure. Bone sarcoma was diagnosed in 12.6% of dogs in this cohort during 71,004 dog-months follow-up. So the Risk for bone sarcoma was significantly influenced by age at gonadectomy.

The male and female dogs that underwent gonadectomy before 1 year of age had an approximate one in four lifetime risk for bone sarcoma and were significantly more likely to develop bone sarcoma than dogs that were sexually intact [RR +/-95% CI = 3.8 (1.5-9.2) for males; RR +/-95% CI = 3.1 (1.1-8.3) for females]. Chi(2) test for trend showed a highly significant inverse dose-response relationship between duration of lifetime gonadal exposure and incidence rate of bone sarcoma (P = 0.008 for males, P = 0.006 for females). This association was independent of adult height or body weight. We conclude that the subset of Rottweiler dogs that undergo early gonadectomy represent a unique, highly accessible target population to further study the gene:environment interactions that determine bone sarcoma risk and to test whether interventions can inhibit the spontaneous development of bone sarcoma.

STUDY 2
http://www.ncbi.nlm.nih.gov/pubmed/11202221
J Pediatr Endocrinol Metab. 2000;13 Suppl 6:1439-55.
Estrogen, bone, growth and sex: a sea change in conventional wisdom.
Grumbach MM.

Source
Department of Pediatrics, School of Medicine, University of California, San Francisco 94143-0434, USA. [email protected]

Abstract
The discovery of a man with a homozygous mutation in the estrogen receptor alpha gene, which results in estrogen-receptor alpha resistance, and of males and females with autosomal recessive mutations in the CYP19 gene encoding aromatase, which leads to a failure to synthesize estrogens, has challenged conventional wisdom about the ‘unimportant’ role of estrogen in the male.

For example, in the male, estrogen (not androgen) derived from direct testicular secretion (approximately 20%) and from extragonadal aromatization of testosterone and androstenedione (approximately 80%), is the critical sex hormone in the pubertal growth spurt, skeletal maturation, accrual of peak bone mass, and the maintenance of bone mass in the adult. Estrogen stimulates chondrogenesis in the epiphyseal growth plate increasing pubertal linear growth. At puberty, estrogen promotes skeletal maturation and the gradual, progressive closure of the epiphyseal growth plate, possibly as a consequence of both estrogen-induced vascular and osteoblastic invasion and the termination of chondrogenesis.

In addition, during puberty and into the third decade, estrogen has an anabolic effect on the osteoblast and an apoptotic effect on the osteoclast, increasing bone mineral acquisition in axial and appendicular bone. In the adult, estrogen is important in maintaining the constancy of bone mass through its effects on remodeling and bone turnover. Establishing a role for estrogen does not exclude a direct action of testosterone on bone in the human male (especially on cortical bone), but this action is less characterized than thought in the past and is relatively minor in comparison with the major effect of estrogen in the male.

STUDY 3
http://www.ncbi.nlm.nih.gov/pubmed/15577502
Clin Orthop Relat Res. 2004 Dec;(429):301-5.
Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury.
Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM.

Source
Texas Tech University Health Sciences Center, Department of Orthopaedic Surgery, 3601 4th St., 4A136, Lubbock, TX 79430, USA. [email protected]

Abstract
To determine whether canine ovariohysterectomy or orchiectomy affects the prevalence of anterior cruciate ligament injury, we compared injury rates of anterior cruciate ligaments of animals that had gonadectomy and animals that were sexually intact as a function of gender, breed, or size. Records of 3218 dogs treated in one orthopaedic veterinary practice during a 2-year period, retrospectively reviewed. Anterior cruciate ligament injury, diagnosed by a history of acute hind limb lameness and by positive anterior drawer test, was confirmed at the time of surgery. The prevalence of anterior cruciate ligament rupture in all dogs was 3.48%.

However, females that had ovariohysterectomy and males that had orchiectomy had a significantly higher prevalence of anterior cruciate ligament rupture than the sexually intact dogs. Larger dogs had an increased prevalence of anterior cruciate ligament injury compared with smaller or medium-sized dogs, with the increased rupture rates for sterilized animals holding across breeds and sizes. Thus. sterilization of either gender increased the prevalence of anterior cruciate ligament injury, suggesting a potential effect of gonadal gender on prevalence of injury of this ligament.

STUDY 4
http://avmajournals.avma.org/doi/abs/10.2460/javma.2004.224.380
Journal of the American Veterinary Medical Association
February 1, 2004, Vol. 224, No. 3, Pages 380-387
doi: 10.2460/javma.2004.224.380

Long-term risks and benefits of early-age gonadectomy in dogs
C. Victor Spain, DVM, PhD Janet M. Scarlett, DVM, PhD Katherine A. Houpt, VMD, PhD, DACVB
Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853. (Spain, Scarlett); Present address: Philadelphia Department of Public Health, Division of Disease Control, 500 S Broad St, Philadelphia, PA 19146. (Spain); Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853. (Houpt)

Objective — To evaluate the long-term risks and benefits of early-age gonadectomy, compared with traditional- age gonadectomy, among dogs adopted from a large animal shelter.

Design — Retrospective cohort study.

Animals — 1,842 dogs.

Procedure — Dogs underwent gonadectomy and adopted from an animal shelter before 1 year of age; follow-up was available for as long as 11 years after surgery. Adopters completed a questionnaire about their dogs’ behavior and medical history. When possible, the dogs’ veterinary records were reviewed. Associations between the occurrence of 56 medical and behavioral conditions and dogs’ age at gonadectomy were evaluated.

Results — Among female dogs, early-age gonadectomy associated with increased rate of cystitis and decreasing age at gonadectomy associated with increased rate of urinary incontinence. Among male and female dogs with early-age gonadectomy, hip dysplasia, noise phobias, and sexual behaviors get an increment, whereas obesity, separation anxiety, escaping behaviors, inappropriate elimination when frightened, and relinquishment for any reason were decreased.