Hypothyroidism and Irregular Periods
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If your periods aren’t like they used to be, you and your doctor might need to do some sleuthing. Irregular periods can be caused by a number of factors, from habits such as extreme exercise to a variety of medical conditions, including hypothyroidism.
Hypothyroidism, a condition in which your thyroid gland doesn’t produce enough hormones, affects nearly 5 percent of Americans 12 and older, and women are more likely to develop it than men, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
Thyroid hormones play multiple roles in your body, such as regulating your energy levels and your internal temperature. When you don’t make enough thyroid hormones, many of your bodily functions slow down. You can experience constipation, fatigue, depression, dry skin, thinning hair, intolerance to cold, muscle cramps, joint pain, and unexplained weight gain, says Rachel McConnell, MD, an assistant professor of obstetrics and gynecology at the Columbia University Irving Medical Center in New York.
Hypothyroidism can also affect your periods by setting off a cascade of hormonal changes that affect your reproductive system.
Here’s what happens: When your thyroid hormone levels decrease, your brain’s hypothalamus starts producing extra thyrotropin-releasing hormone (TRH), and your pituitary gland releases extra thyroid-stimulating hormone (TSH) and prolactin, another hormone.
High prolactin levels then suppress production of gonadotropin-releasing hormone (GnRH) in your hypothalamus. This is a problem, because you need GnRH to produce follicle-stimulating hormone and luteinizing hormone in your pituitary gland. These hormones are important for normal ovarian function, and when hypothyroidism leads to a decrease in their levels, menstrual irregularities may occur, says Dr. McConnell.
Hypothyroidism Can Make Periods Heavy, Absent, or Irregular
Hypothyroidism can put the brakes on ovulation — a phenomenon known as anovulation — resulting in heavy periods. “In some women with uncontrolled hypothyroidism, this anovulation can lead to disordered growth and shedding of the uterine lining, causing unpredictable bouts of heavy bleeding from the uterus,” says Jessica Spencer, MD, a professor and vice chair for education in the department of gynecology and obstetrics at Emory University School of Medicine in Atlanta. “This can be monthly in some women and far apart in others.”
Changes in prolactin levels can thin the uterine lining and change how the pituitary gland controls the ovaries; both can result in periods stopping completely, says Dr. Spencer.
Hypothyroidism can also change how your blood clots, increasing the risk of heavy bleeding, according to the U.S. Department of Health and Human Services Office on Women’s Health.
Women of reproductive age with hypothyroidism may experience heavy periods, absent periods, or irregular periods, says McConnell, and the symptoms of menstrual irregularities will depend on the severity of the hypothyroidism.
“Menstrual irregularities tend to be more common in women with severe hypothyroidism compared to mild hypothyroidism,” says McConnell.
When to Talk to Your Doctor About Your Periods
If your periods are out of whack, you need to find the cause so you can treat it.
Left untreated, hypothyroidism can lead to other complications, such as anemia, low body temperature, and heart disease.
There could also be something else going on altogether.
“Hypothyroidism is only one potential cause of menstrual irregularities,” says McConnell. “There are many causes of menstrual irregularities, such as polycystic ovary syndrome (PCOS), uterine fibroids, infections, and uterine cancer.”
If you have menstrual irregularities, McConnells says to seek medical attention if:
- Your flow is heavy for more than 24 hours
- Your periods are more frequent than 21 days
- Your periods stopped for more than three months (and you are not pregnant)
Your medical provider can perform blood tests to check your levels of various hormones. In hypothyroidism, your TSH level will be elevated and your free thyroid hormone levels will be low.
In some cases, your doctor might recommend a pelvic ultrasound to check for uterine fibroids, polyps, and ovarian cysts, says Spencer. “Depending on the examination and history, further testing may also be warranted to assess for PCOS, another common cause of irregular cycles,” says Spencer. “An endometrial biopsy is sometimes recommended as well to assess for precancerous tissue inside the uterus; this is especially important in women who are obese or have diabetes or hypertension.”
If you already know you have hypothyroidism and have noticed a change in your cycle, see your doctor to make sure your TSH is in the normal range with treatment, says Spencer. If your period does not normalize and your TSH is in the normal range, you should make an appointment with your ob-gyn so they can evaluate you for other causes, she says.
How Hypothyroidism’s Effect on Periods Can Impact Fertility
Hypothyroidism could disrupt your plans to get pregnant. To conceive, you need to ovulate and have a good endometrial lining of the uterus for an embryo to implant.
“Women with hypothyroidism may develop a short luteal phase, which is the time between ovulation and the start of your period,” says McConnell. “If a woman has a short luteal phase, implantation of an embryo may not occur.” You might also have abnormal ovulation or none at all.
Changes in periods do not always mean reduced fertility, but they should be evaluated by a physician if they persist, says Spencer.
“Untreated hypothyroidism may also increase a woman’s risk of miscarriage, so it’s important to have your thyroid checked if you are struggling to conceive or have a history of miscarriages,” Spencer says.
The Benefits of Catching Hypothyroidism Early
There’s an early stage of hypothyroidism called subclinical hypothyroidism, where a blood test for TSH is slightly elevated but the thyroid gland is still producing enough thyroid hormones, says McConnell.
“In our fertility clinic, the most common presentation is subclinical hypothyroidism,” says McConnell.
Subclinical hypothyroidism doesn’t usually disturb periods, but it can still lead to some irregular bleeding and complications in pregnancy, says Spencer. “Eventually, without treatment, subclinical hypothyroidism may lead to overt hypothyroidism, causing more menstrual abnormalities and medical problems,” she says.
Hypothyroidism Treatment Can Help Your Periods Too
The standard treatment for hypothyroidism is the prescription medication levothyroxine (Synthroid), a synthetic version of the thyroid hormones your body is lacking.
“If hypothyroidism is the cause of menstrual irregularities, treatment with thyroid hormone replacement using levothyroxine restores normal thyroid levels, and in turn, the interactions between thyroid hormone and reproductive function will return,” says McConnell.
If you have hypothyroidism, your doctor will check your TSH levels regularly and work with you to ensure you are taking the right amount of medication. “Finding the right replacement dose can take time in some women, and the requirements for thyroid hormone can change with diet, age, pregnancy, and weight gain,” says Spencer.
Reach out to your doctor if you have any new or concerning symptoms.
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