Implantable Hormone Pellets for Testosterone Deficiency in Adult Men

CHAPTER 124 Implantable Hormone Pellets for Testosterone Deficiency in Adult Men



Testosterone is responsible for normal growth and development of male sex organs and maintenance of secondary sex characteristics. As the primary androgenic hormone, its production and secretion are the end products of hormonal and biochemical interactions. Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and controls the pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH regulates production of testosterone by the testes, and FSH stimulates spermatogenesis. Testosterone can be converted in the body either to dihydrotestosterone by 5-α reductase or to estradiol by aromatase. Dihydrotestosterone preferentially binds to androgen receptors and becomes the more active form involved in hair growth and sebum production. Estradiol may be important in maintaining libido and bone mass, but may contribute to truncal obesity and feminine characteristics.


Testosterone deficiency is common, occurring in 1 in 200 men. The prevalence increases with age as testosterone levels decrease and sex hormone–binding globulin levels increase (causing a further decrease in free or bioavailable testosterone). More than 50% of men older than 55 years of age may have low testosterone, increasingly referred to as andropause. Treatment should be considered in all men with testosterone deficiency as long as contraindications do not exist.


Abnormally low testosterone levels are associated not only with sexual dysfunction, but with other comorbid conditions such as lipid disorders, cardiovascular disease, insulin insensitivity, osteoporosis, and cognitive and mood changes. Testosterone deficiency may be a cause of sarcopenia, a condition of aging senescence characterized by muscular weakness and atrophy.


In general, there are two basic types of testosterone deficiency:




Satisfactory replacement of testosterone is possible regardless of the type of deficiency.


Hypogonadism is defined as a free testosterone level that is below the lower limit of normal for young adult control subjects. Age-related decreases in free testosterone were once accepted as “normal.” Currently, they are not considered normal. No agreement exists on the exact normal level of testosterone as men age or the serum testosterone level at which a man loses his sexual function.


The definition of relative hypogonadism is also uncertain. Many men have perfectly normal sexual function even if their testosterone levels decline into the age-adjusted lower normal range. Patients with low-normal to subnormal testosterone levels may warrant a clinical trial of testosterone. The threshold of response to and dosage of testosterone vary with age. If LH is increased and the testosterone level is low, the patient will have decompensated primary testicular failure. Testosterone replacement therapy can be essential to maintain physiologically normal levels. Testosterone replacement improves sexual function and mood, increases lean muscle mass and strength, and decreases fat mass in hypogonadal men.


An effect of testosterone on endothelial function in men is supported by a recent study that reported on the effects of intravascular administration of physiologic doses of testosterone on coronary blood flow in men with coronary artery disease. The results showed an increase in coronary vasodilation and blood flow in the testosterone test subjects.



Health Implications of Testosterone Deficiency


Testosterone deficiency can result in the following:











Men with testicular failure may suffer from sexual dysfunction, as well as osteoporosis, muscle weakness, depression, and lassitude, which is the clinical spectrum of hypogonadism. The sexual dysfunction, especially decreased libido and decreased erectile capacity, often reverses with testosterone replacement therapy. Ideally, testosterone therapy should provide physiologic-range testosterone levels (400 to 800 ng/dL). The variability of response in some patients may be related to comorbid medical illnesses, vascular dysfunction causing erectile dysfunction at the penile level, or psychological factors (Box 124-1).





Diagnosis of Testosterone Deficiency


In symptomatic men, these suggested guidelines may be followed:












Contraindications












Patients in Whom Treatment Requires Careful Monitoring









NOTE: It is important to closely monitor those patients with a family history (i.e., presence in a first-degree relative) of prostate cancer, although the relationship between the cancer and testosterone replacement therapy is controversial. A double-blind, randomized, placebo-controlled trial of 237 men 60 to 80 years of age, conducted in the Netherlands from 2004 to 2005 and published in the Journal of the American Medical Association in 2008 (Emmelot-Vonk and colleagues), showed an increase in lean body mass, a decrease in fat mass, increased insulin sensitivity, and no short-term negative effects on the prostate or on cognition. In a review of the literature by Rhoden and Morgentaler in the New England Journal of Medicine in 2004, prospective studies demonstrated a low frequency of prostate cancer in association with testosterone replacement therapy. The conclusion was that there is no compelling evidence at present to suggest that men with higher testosterone levels are at greater risk of prostate cancer or that treating men who have hypogonadism with exogenous androgens increases this risk. It should be recognized that prostate cancer becomes more prevalent exactly at the time of a man’s life when testosterone levels decline.

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May 14, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Implantable Hormone Pellets for Testosterone Deficiency in Adult Men

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