There are a host of hormones that can affect a man's emotional and physical well-being, but one in particular becomes less reliable after age 60. Thyroid hormone declines with age, and a number of recent studies demonstrate a link between waning thyroid hormones and sexual dysfunction. This includes erectile dysfunction, which is the inability to maintain penile erection [source: Krassas]. The most common problems of low thyroid, or hypothyroid, also include declining sexual desire, but it doesn't stop there. Classic symptoms include weight gain, hair loss, memory loss, constipation and rough, dry skin [source: San Diego Sexual Medicine]. The good news is that with synthetic hormone replacement, these symptoms -- including erectile dysfunction caused by hypothyroidism -- usually reverse themselves.