Menopause Hormone Therapy Side Effects

Post-menopausal hormone therapy (MHT) is reported as the most effective treatment for menopausal symptoms such as hot flashes and cold sweats, and at the same time is a treatment that one hesitates to start because of worry about side effects. In the clinic, the question I receive most is "they say it works well, but isn't it dangerous?" To say the conclusion first, the risks and benefits of hormone therapy differ depending on the age at which you start, the type and dose of the medication, the route of administration, and the individual's health condition. In this article, I will organize the risks and benefits without leaning to one side, and examine together for whom the balance is favorable.

The clearest benefit of hormone therapy is the relief of menopausal vasomotor symptoms. For symptoms such as hot flashes and night sweats, the North American Menopause Society (NAMS, 2022) organizes that it is hard to find a treatment more effective than hormone therapy. Because such acute symptoms go beyond simple discomfort and greatly lower the quality of sleep and daily life, treatment has great meaning in terms of quality of life.

The benefits do not stop at symptom relief. Hormone therapy has evidence-confirmed effects of preventing bone loss and fractures, and it also helps with vulvar and vaginal dryness, dyspareunia, and some urinary symptoms. Also, in the long-term follow-up of the U.S. Women's Health Initiative (WHI) study, a tendency for lower breast cancer incidence was reported in women who had a hysterectomy and received estrogen-only therapy, and a result of reduced colorectal cancer incidence was also observed in estrogen-plus-progestin combination therapy. Thus the benefits span several aspects.

When a woman who has a uterus first starts post-menopausal hormone therapy, bleeding like a period or irregular bleeding can occur. In many cases this is a natural reaction arising in the process of using a progestogen together to protect the endometrium. A woman without a uterus has no need to protect the endometrium, so a different type of medication is used, and such bleeding hardly occurs.

The bleeding pattern of hormone therapy differs by method. Let me organize it in the table below.

Before starting treatment, checking for endometrial abnormality and contraindications with ultrasound is a safe starting point. Since not all early bleeding is normal, if the pattern continues for a long time or the amount is heavy, it is better to check the cause through examination. Please also refer to information on abnormal bleeding around menopause.

In the early stage of treatment, nausea, a sense of weight change, breast tenderness, and discomfort similar to premenstrual syndrome can appear. These commonly arise in the process of the body adapting as the dropped hormones are replenished again, and in clinical experience they appear temporarily only at the beginning in most cases.

Such early symptoms can be relieved by finely adjusting the dose and method of administration of estrogen and progestogen. The most basic principle of medication use is to use the minimum dose that produces the desired effect. Hormone therapy also has standard doses, but because responses differ from person to person even at the same dose, adjustment tailored to the individual is key.

• If there is nausea, you can try changing the timing of taking it or the route of administration
• Breast tenderness is often relieved by dose adjustment
• If irregular bleeding becomes prolonged, endometrial evaluation is reconsidered

Rather than enduring symptoms, adjusting in consultation with your attending physician helps you continue treatment for a long time. The explanation about when hormone therapy is needed can also be a useful reference.

The part most worried about is breast cancer and clot risk. These two risks differ greatly depending on the type of medication and the route of administration, so it is more accurate to look at them separately rather than lumping them as "hormone therapy is dangerous."

Breast cancer risk differs in direction depending on whether it is estrogen-only or progestogen-combined. Synthesizing NAMS (2022) and the WHI study, in estrogen-only therapy no increase in breast cancer risk was observed, or a tendency for it to be lower was even reported, whereas in combination therapy using progestogen together, a small and rare degree of risk increase is reported. This risk is also related to the duration of use.

For clot (venous thromboembolism) and stroke risk, the route of administration is a major variable. The UK NICE guideline (NG23) organizes that oral hormone agents raise clot risk, but transdermal formulations through the skin do not raise clot risk. So for those at high clot risk, for example those with a high body mass index, it recommends considering a transdermal formulation first. NAMS also views in the same vein that a low dose and the transdermal route are in the direction of reducing risk.

One of the most important criteria dividing the risk and benefit of hormone therapy is "when you start." This is commonly called the timing hypothesis. NAMS (2022) organizes that in women who are under 60 or within 10 years of menopause and have no contraindications, the balance of benefit and risk for symptom relief and bone-loss prevention is favorable.

Conversely, in cases of first starting after passing age 60, or starting 10–20 years or more after menopause, the risk is viewed as beginning to outweigh the benefit. This means that even with the same medication, the direction in which the scale tips differs depending on the timing of starting. The point that hormones act protectively in healthy blood vessels but may not in already-damaged blood vessels is explained as the background of this timing hypothesis.

Of course, not everything is decided by the timing of starting alone. The individual's medical history, family history, the presence of contraindications, and the intensity of symptoms must be weighed together. If you examine together menopausal symptoms in general and the diagnosis and prevention of post-menopausal osteoporosis, why timing matters becomes clearer.

Even with the same hormone therapy, risk can be lowered depending on how it is designed. The key is tailoring the variables of type, dose, duration, route of administration, and starting timing to the individual. NAMS (2022) also makes clear that the risk of hormone therapy differs depending on these variables.

In actual practice, we consider the following together.

• Depending on whether there is a uterus, we choose estrogen-only or progestogen combination
• If there is clot risk, we prioritize a transdermal formulation instead of oral medication
• We start at the minimum dose that suppresses symptoms and adjust while watching the response
• We attend to endometrial status and regular checkups before and after treatment

How long to continue hormone therapy has no uniformly set answer, and is decided while periodically re-evaluating benefit and risk. Referring to the guide on the duration of hormone therapy also helps. If symptoms are concentrated in the local urogenital area, there are also options that reduce systemic exposure, such as the safe use of local estrogen.

As the saying goes that knowing yourself and your opponent means winning every battle, when you know in advance what could be a problem and then choose, coping also becomes much easier. Hormone therapy is reported as the most effective treatment for menopausal symptoms, and at the same time is a treatment in which the balance of risk and benefit differs depending on the timing of starting and individual condition. Rather than putting it off out of vague fear, checking which way the scale tips in your situation comes first. If you are worried about side effects, please first read the risks and safety of hormone therapy, and check any questions through consultation.

Written by: Lee Dong-hee Director · Obstetrics and Gynecology Specialist · View medical staff profile

First published November 29, 2023 · Last reviewed May 30, 2026

References: North American Menopause Society NAMS Hormone Therapy Position Statement (2022), UK NICE Menopause Guideline NG23 (published 2015, subsequently revised), U.S. Women's Health Initiative WHI Long-term Follow-up Study (2020)

This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through an examination.