You will get lots of advice from people who feel that neutering is the ONLY option, so I will only address reasons I believe this surgery should not be routinely performed and rather only done when it is in the dog's best interests. Here is a list of the Possible Health Repercussions from Neutering from
www.neutering.org: Possible Health Effects of Neutering
Anesthesia shock and surgical complications (Dogs and Bitches)
Post operative pain and infection (Dogs and Bitches)
Obesity (Dogs and Bitches)
Hypothyroidism (Dogs and Bitches)
Cerebellar Cortical Abiotrophy (Dogs and Bitches)
Loss of estrogen; sex and growth hormone (Bitches)
Intervertebral disk disease (Bitches)
Myasthenia Gravis; muscle weakness (Bitches)
Urinary incontinence (Bitches)
Altered moods leading to nervousness, separation anxiety, and digestive disorders (Bitches)
Vaginal perivulvar dermatitis and recessed vulva (Bitches)
Loss of testosterone; sex and growth hormone (Dogs)
Narrowing of the chest resulting in respiratory disorders (Dogs)
Failure to extrude the penis (Dogs)
Loss of testosterone is directly correlated to: heart disease and myocardial infarction, strokes and cardiovascular disease, senile dementia, osteoporosis and hip fracture.
In human beings testosterone has an important role in the regulation of normal growth, bone metabolism and body composition. Specifically, testosterone deficiency is an important risk factor for osteoporosis and fractures in men. Men with testosterone deficiency have significant decreases in bone density, particularly in the trabecular bone compartment. Testosterone deficiency has been reported in over half of elderly men with a history of hip fracture. Men with testosterone deficiency also have alterations in body composition that include an increase in body fat. Using quantitative CT scans to assess fat distribution, we have shown that testosterone deficiency is associated with an alteration in site-specific adipose deposition with increased deposits in all areas, particularly in the subcutaneous and muscle areas.
Because truncal fat correlates with glucose intolerance and cardiovascular risk, hypogonadism may have important implications with regard to overall health and mortality. In one study, the alteration in skeletal muscle composition was associated with a decrease in muscle strength. Therefore, testosterone deficiency is associated with an enhanced risk for osteoporosis, altered body composition including increases in truncal fat, and, possibly, decreases in muscle performance.
Loss of estrogen leads to an acceleration of the bone-degradation process, which in turn results in a loss of bone mass and a raised risk for incurring bone fractures (osteoporosis). Loss of this hormone also causes violent mood swings, irritability, and depression.
In human beings, a drop in the production of sexual hormones can have considerable consequences for the emotional world of women. Many menopausal women observe a reduction of their general performance, an increasing forgetfulness, an impaired fine motoricity, and a diminution in their powers of memory and of planned, targeted, flexible and adaptable thought. Furthermore, many women display a tendency towards pronounced fluctuations in their mood, and even massive symptoms of depression. Very recent studies indicate that estrogen deficiency also increases the risk for Alzheimer's disease.
The process of aging and the regression of the sexual hormones also involves a degradation of the muscle mass. This results in a deterioration of the coordination of body movements and enhances the tendency for falls. The elasticity of the joints also diminishes. The joints become stiff and painful, especially upon rising in the morning. This is due to the reduction in the production of collagen and a reduced storage of water as a consequence of the estrogen deficiency