Endocrinology is perhaps, the only branch of medicine where stimulation and suppression testing are required as the initial step for biochemical confirmation of the clinical condition as hormone secretion is pulsatile. One of the primary needs for an endocrinologist is a pocketbook that can serve as a guide for performing and interpreting these tests. Unfortunately, there is no single source of these protocols, procedures, and interpretation of these tests in the country or even in the Southeast Asia region. This protocol manual is designed to be a ready reckoner for endocrinologists for performing these tests. Disorders of various endocrine glands, including pituitary, thyroid, pancreas, adrenal, gonads, and bone and mineral disorders, have been addressed. The book includes prerequisites and indications of a given test, principles of the testing, detailed procedure, and interpretation. Participant information and instruction sheets have been included, when applicable, to be given as a handout to patients prior to these tests. The manual contains algorithms (e.g., for approaching cases with hypoglycemia) and interpretation provided in a tabular format. It also lists troubleshooting measures for specific tests, when applicable. Further, clinical case scenarios substantiated by clinical and radiological images have been incorporated in the manual to highlight the procedure and interpretation of these tests in the management of challenging clinical cases. The manual is designed to be a comprehensive yet concise document covering all these aspects. Besides blood-based investigations, procedures which are undertaken in challenging endocrine scenarios, including inferior petrosal sinus sampling, and adrenal venous sampling have been elucidated in a crisp and practical manner.