Disorders of the thyroid gland
Thyroid disorders are mainly of two types: hypothyroidism and hyperthyroidism.
In hypothyroidism, the thyroid gland underfunctions and produces decreased amounts of thyroid hormones T3 and T4. This leads to a slowed metabolism, which commonly presents as fatigue, weight gain, cold intolerance, and constipation.
In hyperthyroidism, the thyroid gland overproduces T3 and T4. This speeds up metabolism and commonly presents as a fast heart rate, weight loss, sweating, and anxiety.
Patients with hypothyroidism need thyroid hormone supplementation to support normal metabolism. Available medications include synthetic T3, also known as liothyronine (Triostat, Cytomel), and synthetic T4, also known as levothyroxine (Synthroid, Unithroid, Levoxyl). Iron, calcium, and antacids can interfere with the absorption of levothyroxine.
Desiccated thyroid is derived from the thyroid glands of pigs and is sold under the brand names Armour Thyroid and Nature-throid. Adverse effects are typically due to overdosing and present with symptoms of hyperthyroidism.
T3- and T4-containing medications should be taken on an empty stomach, preferably at the same time every day.
Hyperthyroidism is characterized by excessive production of thyroid hormones. Methimazole (Tapazole) and propylthiouracil (Propacil) are used to treat hyperthyroidism, for example in Grave’s disease. Both propylthiouracil and methimazole decrease the production of new thyroid hormone.
Common adverse effects of methimazole include nausea, rash, joint pain, and hair loss. Serious adverse effects such as agranulocytosis (severely decreased white blood cell count) and liver toxicity may occur. Methimazole is contraindicated in the first trimester of pregnancy due to teratogenicity.
Propylthiouracil adverse effects include rash, loss of taste, headache, hypersensitivity, renal dysfunction, jaundice, and hepatic failure. Rarely, agranulocytosis may occur.
Both methimazole and propylthiouracil increase the effect of warfarin and may cause bleeding.
Radioactive iodine: Radioactive iodine, called I-131, is sold under the brand names Iodotrope, i3odine Max, and Hicon. It is used to treat hyperthyroidism and thyroid cancer. To avoid radiation exposure, radioactive iodine should not be used in pregnant and nursing women. Treatment with radioactive iodine will eventually cause hypothyroidism.
Medications used to treat disorders of the reproductive system
Androgens and testosterone: Androgens are hormones produced predominantly by the testes, ovaries, and adrenal glands. Some are naturally occurring, while others are synthetic.
Androgens are used to help with fertility issues, increase muscle mass, provide hormone replacement in hypogonadism and other conditions, and treat endometriosis and certain types of breast cancer.
The most commonly used androgen is testosterone (Testim, Androgel, Depo-testosterone, Fortesta, Xyosted, Jatenzo, Aveed). Other androgens include methyltestosterone (Methitest, Android, Virilon), fluoxymesterone (Androxy, Halotestin), dihydrotestosterone or androstanolone (Andractim), danazol (Danocrine), DHEA, and testolactone (Teslac).
Synthetic versions of testosterone are known as anabolic steroids, for example Testim, Androgel, danazol, fluoxymesterone, mesterolone, methyltestosterone, nandrolone (Durabalin), oxandrolone (Oxandrin), and oxymetholone (Anadrol).
Testosterone is available as injection, gel, tablet, capsule, pellets, patch, implant, and solution forms.
Adverse effects include acne, hair loss, enlargement of the prostate gland, polycythemia (increased red blood cell count), virilization in females (deepening of voice, enlarged clitoris, hirsutism), jaundice, and mood changes.
Contraindications include prostate cancer, pregnancy, and severe heart disease. Testosterone is a controlled medication under Schedule III due to its potential for abuse.
Estrogens: Estrogen is a naturally occurring hormone produced primarily by the ovaries, with smaller amounts produced by the adrenal gland and fat cells. Women have high levels of estrogen during their reproductive years. Smaller amounts are also present in men and contribute to reproductive health, metabolism, bone density, cardiovascular health, and brain health.
The three naturally occurring forms of estrogen are estradiol (E2), estrone (E1), and estriol (E3). Synthetic versions include ethinyl estradiol, conjugated estrogens, estradiol valerate, esterified estrogens, and estropipate.
Synthetic estrogen is used as hormone replacement therapy to treat menopausal symptoms, osteoporosis, ovarian failure, and certain breast and prostate cancers. It is available as tablets, capsules, cream, gel, patch, sprays, injections, vaginal suppositories, and rings.
Commonly available brands include Alora, Climara, Bivigel, Botti, Estrace, Estraderm, Yuvafem, Vagifem, Premarin, Femring, Ogen, and Estring.
Adverse effects include breast tenderness, nausea, headache, weight gain, abnormal uterine bleeding, and rarely, stroke, jaundice, blood clots, and heart attack. Unopposed estrogen may cause endometrial cancer.
Diethylstilbesterol (DES) is a synthetic form of estrogen that is rarely used now because it has been shown to cause birth defects and vaginal and cervical cancers in progeny after intrauterine exposure.
Estrogen and progestin combinations: Progesterone is a hormone produced by the ovaries and placenta. Along with estrogen, it is essential for reproductive health in females.
Many types of synthetic progesterones, also known as progestins, are available, including desogestrel, levonorgestrel, megestrol, norethisterone, and medroxyprogesterone.
Combination drugs containing estrogen and progesterone are commonly used as birth control pills (oral contraceptives) and as hormone replacement therapy (HRT) to treat menopausal symptoms, acne, menstrual cycle regulation, and osteoporosis.
Commonly available brands include Estarylla, Yaz, Femynar, Mili, Vylibra, Previfem, Nymyo, Yasmin, Loryna, Delyla, NuvaRing, and Xulane.
Adverse effects include nausea, change in bowel habits, weight fluctuations, irregular bleeding, headache, blood clots, depression, and tumors in the liver.
Using oral contraceptives increases the risk of heart attacks, stroke, and blood clots in cigarette smokers and those older than 35 years of age.
Taking birth control pills with certain supplements like St. John’s wort may cause contraceptive failure by decreasing the levels of estrogen and progesterone.
Emergency contraception: Emergency contraception includes copper intrauterine devices (IUDs) and emergency contraceptive pills (ECPs).
ECPs include ulipristal acetate in a single dose, levonorgestrel in a single or two split doses, and combined ethinyl estradiol and levonorgestrel in two doses. ECPs need to be administered within 3-5 days of unprotected sexual intercourse.
Ulipristal blocks the effect of progesterone and is a selective progesterone receptor modulator. Common brand names include Ella for ulipristal and Plan B, Plan B One Step, EContra EZ, My Way, and Next Choice for levonorgestrel-containing ECPs.
5 alpha reductase inhibitors: These drugs block the enzyme 5-alpha-reductase, which converts testosterone to dihydrotestosterone (DHT). DHT is normally involved in the development of male external genitalia, male pattern hair distribution, and prostate growth.
These drugs are used to treat BPH (benign prostatic hyperplasia) and male pattern baldness. Examples include finasteride (Propecia, Proscar) and dutasteride (Avodart). Adverse effects include impotence, gynecomastia, and decreased libido.
Aromatase inhibitors: The enzyme aromatase converts androgens into estrogens. Aromatase inhibitors block aromatase and reduce estrogen levels.
They are used in the prevention and treatment of estrogen receptor (ER) positive breast cancers. Examples include anastrozole (Arimidex), letrozole (Femara), exemestane (Aromasin), and fadrozole (Afema). They may cause muscle pain and stiffness, skin ulcers, insomnia, hot flashes, jaundice, sexual dysfunction, and osteoporosis.
Selective estrogen receptor modulators or SERMs: SERMs affect the action of estrogen on tissues such as breast and bone. Several types are available, for example tamoxifen (Nolvadex, Soltamex, Tamofen), raloxifene (Evista, toremifene (Fareston), and clomiphene (Clomid, Serophene).
Uses are guided by specific tissue effects. For example, tamoxifen and raloxifene are used to treat and prevent breast cancer, raloxifene is used in osteoporosis, toremifene is used in metastatic breast cancer, and clomiphene is used to treat infertility in PCOS (polycystic ovarian syndrome).
Adverse effects include hot flashes, night sweats, irregular periods, decreased libido, blood clots, uterine cancer, and stroke.