The most common route of administration for testosterone is by intramuscular injection. However, it has been reported that AndroGel, a transdermal gel formulation of testosterone, has become the most popular form of testosterone in androgen replacement therapy for hypogonadism in the United States. Non-medical use
Athletics
Testosterone is used as a form of doping among athletes in order to improve performance. Testosterone is classified as an anabolic agent and is on the World Anti-Doping Agency (WADA) List of Prohibited Substances and Methods. Hormone supplements cause the endocrine system to adjust its production and lower the natural production of the hormone, so when supplements are discontinued, natural hormone production is lower than it was originally.Anabolic–androgenic steroids (AAS), including testosterone and its esters, have also been taken to enhance muscle development, strength, or endurance. They do so directly by increasing the muscles protein synthesis. As a result, muscle fibers become larger and repair faster than the average persons.After a series of scandals and publicity in the 1980s (such as Ben Johnsons improved performance at the 1988 Summer Olympics), prohibitions of AAS use were renewed or strengthened by many sports organizations. Testosterone and other AAS were designated a "controlled substance" by the United States Congress in 1990, with the Anabolic Steroid Control Act. Their use is seen as an issue in modern sport, particularly given the lengths to which athletes and professional laboratories go to in trying to conceal such use from sports regulators.
Nasal congestion is the blockage of nasal breathing usually due to membranes lining the nose becoming swollen from inflamed blood vessels. Background
In about 85% of cases, nasal congestion leads to  mouth breathing rather than nasal breathing. According to Jason Turowski, MD of the Cleveland Clinic, "we are designed to breathe through our noses from birth—its the way humans have evolved." This is referred to as "obligate nasal breathing. "Nasal congestion can interfere with hearing and speech. Significant congestion may interfere with sleep, cause snoring, and can be associated with sleep apnea or upper airway resistance syndrome. In children, nasal congestion from enlarged adenoids has caused chronic sleep apnea with insufficient oxygen levels and hypoxia, as well as right-sided heart failure. The problem usually resolves after surgery to remove the adenoids and tonsils, however the problem often relapses later in life due to craniofacial alterations from chronic nasal congestion. Causes
Allergies, like hay fever, allergic reaction to pollen or grass
Common cold or influenza
Rhinitis medicamentosa, a condition of rebound nasal congestion brought on by extended use of topical decongestants (e.g., oxymetazoline, phenylephrine, xylometazoline, and naphazoline nasal sprays)
Sinusitis or sinus infection
Narrow or collapsing nasal valve
Pregnancy may cause women to suffer from nasal congestion due to the increased amount of blood flowing through the body. Nasal polyps
Gastroesophageal reflux disease (theorized to cause chronic rhinosinusitis- the "airway reflux paradigm")
COVID-19

Nasal obstruction
Nasal obstruction characterized by insufficient airflow through the nose can be a subjective sensation or the result of objective pathology.