Graves’ Disease affects Missy Elliot: What is it?

Missy Elliot fans have waited six years for a new album, and now they know why. Thursday, rapper and producer has revealed that she suffers from Graves' disease, a disease that affects the autoimmune system and thyroid gland.

Elliott told People magazine had the disease, even simple daily tasks difficult for her. "I could not write because my nervous system was so bad - I could not even use a pen," she said.

The ominously named disease is not familiar to most people. We explain what you need to know about Graves' disease below.

What causes Graves' disease?

Graves' disease happens when too much thyroid hormone is produced, a condition called hyperthyroidism, according to the Mayo Clinic. This high level of thyroxine can dramatically increase the metabolic rate of your body, which can affect weight, mood and energy.

What are the symptoms?

The symptoms are not pretty: rapid heart rate, tremors, double vision, insomnia, fatigue, muscle weakness, anxiety, and in men, enlarged breasts. The list is long. Elliott, 39, says she has suffered hair loss, mood swings, and loss of muscle control since she was diagnosed with the condition three years ago.

How can it be treated?

Elliot said radiation and time in the gym helped her get better. Other treatments include anti-thyroid drugs and doses of radioactive iodine to shrink the gland. If left untreated, Graves' disease gets worse over time. However, if diagnosed correctly as was Elliot, a person can continue living a normal life for most. Elliot is now meeting with Timbaland for several new songs, and his highly anticipated seventh album, Block Party, is on its way.

President George HW Bush and First Lady Barbara Bush has also suffered from Graves' disease. Read about how this affected their lives here.