It is suggested that bioavailable testosterone represents the fraction of circulating testosterone that readily enters cells and better reflects the bioactivity of testosterone than does the simple measurement of serum total testosterone. Also, varying levels of SHBG can result in inaccurate measurements of bioavailable testosterone. Decreased SHBG levels can be seen in obesity, hypothyroidism , androgen use, and nephritic syndrome (a form of kidney disease ). Increased levels are seen in cirrhosis , hyperthyroidism , and estrogen use. In these situations, measurement of free testosterone may be more useful.
If testosterone deficiency occurs during foetal development, then masculinisation of the foetus will fail to occur normally and this may give rise to disorders of sex development. If testosterone deficiency occurs during puberty, a boy’s growth may slow and no growth spurt will be seen. The child may also fail to develop full sexual characteristics (hypogonadism) associated with men undergoing puberty, including development of pubic hair, growth of the penis and testes and deepening of the voice. Around the time of puberty, boys with too little testosterone may also have less than normal strength and endurance, and their arms and legs may continue to grow out of proportion with the rest of their body.