Basically a thyroid gland highly related with body metabolism. And it produces such hormones like T3 & T4. As thyroid glands have much responsibility to care & produce some of main hormones in female genital parts, when there is overactive or underactive thyroid problems with female, it affects their menstrual cycle periods badly. Due to variance levels of hormones in the body, it leads to early puberty or delayed puberty in girl's life and also makes irregular often period times with ladies.
Hypothyroidism & Hyperthyroidism sometimes followed by genetic or their body condition to their children. So in early age like before 11 years old a small girl will attend her puberty because of thyroid problem and menstrual periods for a girl is been started in very early age. Some of girls also facing the problem that not getting their menstrual periods after teenage also because of the hypothyroidism.
Patchy periods, often period times, late period times also have linkage between hypothyroidism. In these times, a girl will face heavy menstrual bleeding for hour by hour for very long time with continuous stomach pain which is intolerable. Symptoms are like wounding pain, heavy back pain, joint leg pain, sluggishness, tired feel, headache etc. As basically thyroid affects the female ovulation and its genetics production, it will cause problems in milk secretes in breast and healthy ovulation egg problems in fertility times.
Actually your stress and weight loss only mostly stops your regular periods. As endocrine controls the menstrual periods and thyroid hormones production affects endocrine, some of girls are advised to take regular pills for right period times even in their thyroid problems. Menstruating problems continues even after 40 ages also. Thyroid medicines followup advised by doctors, Radiation surgeries to balance hormones levels, Calcium & iron vitamins healthy foods, and proper food diet will give your better results for proper periods. You should check your T4 and TSH levels often for your health condition. Doctors are saying that T4 level is 1.7 and TSH level is 0.10-5.50 are proper.