The most common symptoms of an underactive thyroid gland are:
Feeling tired or low
Dry skin
Gaining weight
Feeling the cold
Constipation
If you're a woman, irregular periods.
If an underactive thyroid isn't treated, your symptoms may gradually get worse. After a few months or years, you may notice you:
Have very dry, flaky skin
Have coarse hair
Gain weight, even though you're not eating any more
Feel depressed
Feel sluggish and find it difficult to think clearly
Have a hoarse voice
Lose some of your hair.