Follicle Stimulation / Ovulation Induction
Follicle stimulation (ovulation induction) is the use of medicines to help follicles grow and to bring about ovulation. Clinicians use it when ovulation in a cycle is absent or weak. Patients often use the terms "fertility drugs" or "fertility medications" for them.
These drugs fall into two main types. The first type is oral tablets, such as clomiphene citrate and letrozole. Clomiphene is a selective estrogen receptor modulator. Letrozole is an aromatase inhibitor. The second type is injected gonadotropins, which contain FSH alone or FSH combined with LH.1
The right type depends on the ovulation problem, the clinical method in use, and how the cycle is monitored.2 A 2014 randomized trial in the New England Journal of Medicine compared letrozole with clomiphene. It studied women who did not ovulate because of polyendocrine metabolic ovarian syndrome (PMOS), formerly polycystic ovary syndrome (PCOS). Letrozole led to more live births.3
A restorative evaluation asks one question first: why is ovulation not occurring? Anovulatory cycles, cycles without ovulation, have distinct causes. These causes include insulin resistance and PMOS / PCOS, thyroid disorders, and high prolactin (hyperprolactinemia). Stress or low body weight can also disrupt the hypothalamus, the brain region that signals the ovaries. Other causes exist as well.4
Charting the cycle with a fertility awareness-based method shows the pattern over time. A single hormone blood test cannot show that pattern.5 Treating the metabolic cause can restore ovulation on its own. One example is treating insulin resistance in PMOS / PCOS with an insulin sensitizer. Drugs designed to force ovulation, such as clomiphene or gonadotropins, may then not be needed.26
When stimulation is necessary, named methods such as NaProTechnology choose the drug and the monitoring plan. They base that choice on the specific ovulation problem and not on a single set protocol.7
Close monitoring of the cycle during stimulation is standard. A follicle maturation study tracks the growth of follicles. It detects a poor response early and guides the decision to add an HCG trigger.8 Monitoring also lowers the risk that several follicles mature at once.9
Restorative protocols aim for one well-developed follicle. This aim favors single pregnancies over twins or higher multiples.10 Retrieval-based protocols grow many follicles on purpose, because the eggs are collected rather than ovulated.
ART protocols use controlled ovarian stimulation. This process grows many follicles so that the eggs can be collected rather than ovulated. The drug names may be the same. The doses are much higher, because the goal is egg collection rather than support of one ovulation for the couple.11
The restorative aim is one well-timed ovulation. Retrieval-based stimulation bypasses the process that failed without correcting the reason it failed.10 See IVF vs. RRM for a side-by-side comparison of the two.
Cited in this entry
- Quaas AM, Legro RS Pharmacology of medications used for ovarian stimulation. Best practice & research. Clinical endocrinology & metabolism. 2019. https://pubmed.ncbi.nlm.nih.gov/30470497/
- Balen AH, Morley LC, Misso M, Franks S, Legro RS, Wijeyaratne CN et al. The management of anovulatory infertility in women with polycystic ovary syndrome: an analysis of the evidence to support the development of global WHO guidance. Human reproduction update. 2016. https://pubmed.ncbi.nlm.nih.gov/27511809/
- Legro RS et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. N Engl J Med. 2014. https://rrmacademy.org/library/letrozole-or-clomiphene-for-infertility-in-the-polycystic-ovary-syndrome-recgrvvtlvs9dogjt/
- Concepción-Zavaleta MJ, Coronado-Arroyo JC, Quiroz-Aldave JE, Durand-Vásquez MDC, Ildefonso-Najarro SP, Rafael-Robles LDP et al. Endocrine factors associated with infertility in women: an updated review. Expert review of endocrinology & metabolism. 2023. https://pubmed.ncbi.nlm.nih.gov/37702309/
- Hilgers TW The Identification of Postovulation Infertility with the Measurement of Early Luteal Phase (Peak Day +3) Progesterone Production. The Linacre quarterly. 2020. https://pubmed.ncbi.nlm.nih.gov/32431450/
- Costello MF, Eden JA A systematic review of the reproductive system effects of metformin in patients with polycystic ovary syndrome. Fertility and sterility. 2003. https://pubmed.ncbi.nlm.nih.gov/12524053/
- Hilgers TW. Chapter 46: Medical Treatment of Ovarian Dysfunction. In: The Medical and Surg. https://rrmacademy.org/library/chapter-46-medical-treatment-of-ovarian-dysfunction-reczvqrk2hqh6vuvk/
- Hilgers TW. Chapter 22: Disorders of Human Ovulation: Clinical Validation of the Sonograph. https://rrmacademy.org/library/chapter-22-disorders-of-human-ovulation-clinical-validation-of-the-sonographic-recrswdffxlqybddl/
- Child TJ, Barlow DH Strategies to prevent multiple pregnancies in assisted conception programmes. Bailliere's clinical obstetrics and gynaecology. 1998. https://pubmed.ncbi.nlm.nih.gov/9930294/
- Boyle PC, de Groot T, Andralojc KM, Parnell TA. Healthy singleton pregnancies from restorative reproductive medicine (RRM) after failed IVF. Frontiers in Medicine. 2018. https://pubmed.ncbi.nlm.nih.gov/30109231/
- Huirne JA, Lambalk CB, van Loenen AC, Schats R, Hompes PG, Fauser BC et al. Contemporary pharmacological manipulation in assisted reproduction. Drugs. 2004. https://pubmed.ncbi.nlm.nih.gov/14871171/
Authoritative references
How other clinical authorities define this term. RRM Academy curates these verbatim or under fair use so the medical consensus is visible alongside our RRM-contextualized definition above.
- MeSH D010062
Techniques for the artifical induction of ovulation, the rupture of the follicle and release of the ovum.
- Wikipedia Ovulation_induction
Ovulation induction is the stimulation of ovulation by medication. It is usually used in the sense of stimulation of the development of ovarian follicles to reverse anovulation or oligoovulation.
This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.
